I haven't used painter essentials so I can't give you any comparison notes.
However, apparently there's a humble bundle for Corel painter. Might save you even more money!
https://www.humblebundle.com/software/painter-create-with-confidence
As for your questions
Does anyone have Painter 2019 and how do you like it?
-It's fine. It can do pretty much everything you need a painting software to do. Is it mind blowing? No. Does it work? Fairly well. No big complaints. I'm used to it and I'm fast with it, so it's what I like to use.
If I bought it I could get it even if I don't have a previous Painter?
-What your buying should say 'upgrade' or 'full version'. I have no idea if you can upgrade painter essentials to painter 2019. So if it's an 'upgrade', then no, you can't use it if you don't have a previous version of painter. 'full version' then yiss.
When I move to a different computer/laptop/tablet (surface for ex) will I be able to
not re-buy the program? As I bought it can I move it as I move systems?
Yup. Pretty sure you can. As long as you don't lose the key it should be fine.
If you've got anymore questions lemme know