hello! i had this post saved when i was in vacation in order to reply so here we go!
First of all i wanna say that this is a very well written post and i had never thought this perspective. As you say the more power you have and more money your vote worth, if you upvote someone it may be consider as a "why did he deserve a vote like this, i have more quality posts than him" and this is a continuous loop.
What i try to do with my upvote power is to firstly upvote the ones i follow. There is a reason as why i follow them and that is that i consider them as quality posters, they are active ones, they comment back, i like their posts and there is an interaction going on.
By quality poster (because there is no correct answer to that) i consider the ones that have the qualities i said above as well as the ones who don't upload only a single picture,meme or sentence.
Sadly i can't even provide all of them a decent upvote as my vp decreases fast. I mostly can give them by the prices now, around 2-3 cent of vote and sometimes i may cast some 100% votes that are about 10 cents. If i have vp after that then i try to find random people that i like their posts like i did with you and upvote their content and if possible add them in my following list.
If i were in your situation because i try to manually upvote everything too and had that amount of sp i would use some autovoting services to provide some people i like some constant support. That doesn't mean though that i would use 100% of my voting power to them cause later on i can't manually upvote anything so instead if you votes worth let's say 5$ i would give them 50 cents or 1$ if it wort 20$ then 5$ always depended on how much active i am in manually voting.
Then everyone will be happy. Note that the ones you consider as your friends, loyal followers etc etc that you would use on the autovoting services won't have any hardfeelings towards you if your vote is half or 1/3 on your 100% power. they will be instead happy that you support them constantly!