I suggest starting with FR. The main reason is because the pace of play will be more like what you're already used to from tournaments. For a while at least, you'll have to focus part of your attention on identifying when and why you should do things differently from tournaments. Until this becomes reasonably natural, I'd lean away from adding even more to think about by going to 6max.
As for choosing tables, find out what's most comfortable for you (or least uncomfortable). If you find you're okay with lots of players to the flop and or larger avg pot size, fine. But if you discover you feel better at other types of tables, look for them. It's not like the choice you make now can't be changed as you get used to cash and your game improves.
Psychologically, if limiting your risk is part of why you play tournaments, you might want to look for tables that offer lower variance rather than greater potential profitability. Again, you can change as you get used to cash play.