The topic title might be a bit vague, since it's impossible for this port to be 1:1 arcade accurate when it's not even trying to be, what with the additions of the Super Stage, Yashoo, the Leo Prototype and smaller horizontal area. What I mean is solely related to the number values (scores, time outs) and some of the inaccuracies present in the current demo (Dops giving you 5k points for each kill is what made me do this). I also never used the forum feature of Itch, so I am not sure where this would go, so I put it in general just to be safe.
Score Values (names taken from R-Type Wiki)
Stage 1 Enemies:
Pata-Pata - 200
Bink - 200
Scant - 500
Bug - 200
Cancer - 300
P-Staff - 500
Blaster - 100
Shell - 200 per destroyed part (it should fire at the player only when they enter it, not before)
Tabrok - 800
Stage 2 Enemies:
Baldur - 700
Gouger - 500
Wick - 100
Zoido - 500
Stage 4 Enemies:
Cytron - 400
Geld - 200
Stage 5 Enemies:
Cheetah - 800
Mid - 400
Pursuer - 300
Slither - 800 for head, 300 for body parts
Stage 6 Enemies:
Newt - 300
Dop - 1000
Stage 7 Enemies:
Boldo - 1500
Sonar - 400
Fast - 200
Stage 8's Only Enemy:
Mikun - 200
POW Armor - 200
Power-up Picked Up - 400
Bosses:
Dobkeratops - 300 for each of the blue "orbs," 5000 for destroying it (yes, you can destroy the "orbs")
Worm - 200 per destroyed part
Cyst - 8000
Compiler - 5000 per destroyed part
Bellmite - 300 per destroyed organic pod surrounding it, 2000 for destroying the main body
Yashoo - 10000
Bronco - 100 for ceiling junk, 10000 for junk Bronco tosses
Destroying Bronco doesn't give any score. When it's destroyed, anything left on screen is destroyed as well and counted towards your score, which is what every boss does.
Bydo Core - 15000
Warship:
Main Engine - 800
Standard Gun Tower - 200
Multiple Gun Tower - 700
Large Gun Tower - 300
Laser Tower Block - 800
Spare Engines - 600
Front Fort - 400
Particle Inhaler - 600
Space Navigation Radar - 600
Core - 10000
Any damage done to the battleship outside of these mentioned parts gives 600 points.
The Master System Hidden Stage score values are unknown and probably too high in the original (you get 100k for beating the boss).
I would say the score should be like this to keep it somewhat close to arcade score values (the enemies have no official names, only the boss does):
"Globin" (spawned from the flesh serpents) - 100
"Weed" - 100
"Grasshopper" - 400
"Dragonfly" - 400
"Proto-Bydo Force" - 200
"Yellow Guy" - 200
Helger (Stage Boss) - 10000
He should time out after 1 minute 30 seconds (in the original game, due to slowdown it's not entirely clear how long it is, but that time seems plausible if all slowdown was removed, with slowdown it takes around 2 minutes for it to time out). Also in the original, he takes damage to the flashing brain, not the mouth, but I prefer the mouth over the brain, to be honest, since R-Type is all about finding weaknesses and the mouth makes more sense than a brain. I'm also not entirely sure about the orbs it hurls gave score in the original SMS version, because none of the other destructible projectiles give any score whatsoever, I'll leave that one up to you.
Stage 6 Inaccuracies:
When the 3 Dops appear from the bottom (the kinda tube-ish section after the start of the stage), the Dop that comes from the top once the Dop, that goes to the right and down should come on the screen slightly after the previous one and not be sandwiched together.
The first fast center Dop before the Dop Rush (the area with the POW Armor, that gives you laser) needs to be faster, to catch people off guard. Also, when entering the Dop Rush arena, there is one more Dop, that comes from behind to catch you off guard.
Dop Rush before Yashoo (weakspot positions): L,L,L,L,L,L,L,L,R,L,L,R,L,L,R,L
You can't go completely right, but that means that you can easily pull off the Yashoo safespot, as you can't mess it up by running into the scenery or the boss itself like in the original PC Engine version.
Boss timeouts (they are so inconsistent between one another in the original arcade version, but the bosses don't time out in the MD demo, that's a big nono):
Dobkeratops - after the weakspot gets activated, once 43 seconds pass, the blue orbs get destroyed and starts moving to the left, it then takes 21 seconds before the game considers the stage complete and gives you invulnerability (Dob gets stuck in the hole). You might want to make the "stage clear" timer slightly shorter due to the zoomed in screen.
Cyst & Worm - After the Worm enters Cyst for the first time, the boss gets properly activated and it takes 1 minute 40 seconds for it to time out.
Warship - Times out after 1 minute 20 seconds. When the boss music starts, 48 seconds in the Front Fort gets respawning guns, which are milked for score, then after 32 seconds the boss timeouts and the stage is considered complete, as it gives you invulnerability. However, you still have 6 seconds to destroy the core before it sinks into the floor. It starts sinking when it is at the top of the screen, once it sinks, you can't destroy it (well, technically you can, but it's extremely precise even with the invulnerability).
Compiler - Times out after two minutes after it enters from the left, which takes 6 seconds
Bellmite - Times out after 58 seconds, you don't get invulnerability when it happens, as it leaves and fires out any remaining orbital pods in all directions, which can kill the player, that lasts 3 seconds.
Yashoo - Timeout happens after 2 minutes when the wall core activates. The core keeps on moving when it moves up and down and when it's in the center, the core is exposed for about 22 frames (about 0.36 seconds), meanwhile when it stops at the top or bottom, it is exposed for 2 seconds. The top and bottom part should also activate sooner, because in the original PCE version, it takes 3 seconds before the core is activated and shown on screen.
Bronco - Times out after 1 minute when Bronco comes it, the first 10 seconds of the fight when the boss theme starts is dealing with ceiling junk and Sonars. The bigger question will be if the safespot will even be possible to do on the MD version.
Bydo Core - Times out after 1 minute 35 seconds.
After 1 minute 12 seconds, the 4 Wins (the whirlpool projectiles) become homing, the last 23 seconds either results in dying to them or surviving if you have max speed. Might need to be adjusted due to smaller play area, due to how the Bydo Core takes up half the screen. It also doesn't open up again after it fires out the third Win, so you can't shoot the Force Pod into it and kill it, you either die to the homing Wins or survive with high speed.
Lastly, the stage music doesn't fade when entering bosses (with the exception of the Bydo Core).
The port is already impressive in an of itself and I wish you the best of luck.