I think you should absolutely write to a man you are interested in if he states what he is looking for and you can truthfully say you meet that criteria. I give a woman extra points for reaching out because most do not like to initiate.
I would stay stay away from any guy who says he wants to be friends first. He’s either lying or he shouldn’t be on a dating site. He should be on meetups.com
As far as paid or non paid I do both and they both seem to fluctuate. You should probably do one of each.
I’m about 0-20 finding someone I want to go on multiple dates with so I definitely don’t think 10 is unreasonable.