At wits end, can anyone answer this insane question about emptying your bath?!

[Unsersop]

I am certain the bath is draining slowly. However, now I am confused because I put some drain stuff down and I can’t tell if it’s still blocked. When I run the taps with the plug undone, the bath doesn’t fill but it does cover the plug and fills a tiny bit if you see what I mean? Is that normal? Or should it all disappear immediately as it pours in when the plug is out?

Asking as we have a potential bigger drain issue and so hoping it isn’t related.

Probably a hair blockage. Make sure to pull hair out of the plug hole after every use, or at least every other day.
Or buy one of those long spring things for cleaning out plug holes, they're very handy, but don't get it stuck!

get a ..pokey stick...(like a longinsh thin nuff to go down a pook hole)push in.e
xtract.
yuk.?
skoosh wd 40 n put plug in.

I use drain unblockers like grotbuster but sometimes have to do it twice. Leave it in as long as you can both times