I've never played at Unibet but I just reloaded at BetOnline and dabbled in their cash games and there tend to be plenty of fish so the games are fairly soft which is what you look for when playing cash games. Good luck with whatever site you choose perhaps somebody can tell you about Unibet so you can better decide between the two.
Depends what you want. I would suggest party poker because HUD is not allowed which in my eyes is a good thing. Level playing field is important. But there seem to be far stronger players there now, even at low stakes. The action is usually too slow for me.
Stars has the most players but cash tables at low stakes can be really stupid. I have struggled to make anything there. What you gain on one day you usually lose quickly.
Id personally go with ignition, you are anonymous so there won't be any tracked stats on you. That way you can focus on your own game and gain an ability to get a read on someone else's game fairly quickly. Also since it is also a casino and sportsbook rolled into one, you'll get a decent amount of soft competition coming in.
of course great importance the place where you play, the number of weak players at the table, structure rake, rakeback and such things, but the most important what you should concentrate on is your game, fix all your mistakes, improve weaknesses, diversify the techniques used to on any pitch you could compete. And remember the main thing, you will earn money in games with weak players, and getting stronger - with strong players.
it is advisable to play on a site which has as few regular players and as many fish as possible. like for example unibet, betclic.fr or pmu.fr which are sites where people play there in order to be able above all to bet on sports bets.