question about tag etiquette + sideblogs!

i've been on tumblr for a while but it's not my main social media, so i'm not as familiar with how it works as well as other sites i use..

i occasionally post on there so of course i have organization tags on my blog. my question is that... is it considered rude at all to ONLY tag reblogged art with a reblog tag? i guess it's a silly question because i don't get upset when someone reblogs my art and does that, but it just has me worried. i'd love to leave comments on each piece of art i reblog but i can only say "I LOVE THIS SO MUUUCH" in so many ways that feel unique to the post i'm reblogging...

second question - this is also a bit silly but i can't remember, if you have a sideblog and like/rb/whatever on other posts, does the other user see your main blog? i wanted to start a roleplay blog but i'm admittedly a little embarrassed about it and would like to keep it fully separate from my main.. would i need a separate account for that? :')