The “strip immediately” options (from Talk or the toggle in customize) are just for them to strip right then. If you want them to remain nude, you have to brand them and use the nudity rule (like in vanilla). The tooltip from hovering over the customization toggle button should explain that as well as the nudity rule toggle (if unlocked via brand).
Lip sizes do add lisps if at the extreme side of the scale, but reducing doesn’t immediately remove lisps. I believe there’s a chance every day, but the quickest way is to just the lab to remove it (as it is a physical trait).
If you mouse over the left side of the character names, it shows the character’s body image.
Something may be broken on your save if you can’t open your self-inspect menu. I haven’t heard of or seen a bug around that in this version. It may be fixable though. If you aren’t already, download and start the game with the debug exe. See if you’re getting an error when trying to open self-inspect in that. We may be able to talk you through fixing the save, though if it’s just a mid installation it may also work if you just reinstall it fresh and reattempt the save.