1. Cheating is a mindset thing. It never appealed to me since I'm grownup and there has never been a reason to stop. However, what I do is play with reduced damage and saving because I like to try different things. I would hardly take any risks if it weren't for saving. Reduced damage because I'm not an FPS kind of person and more into the strategic aspects of the game.
I find that with these settings there is essentially no need to use any cheats at all.
2. After so many years you should know if you wish to use any mods. After a longer pause i find Native Warband entertaining.
3. Depending also on the size of your group and your equipment. You can even take recruits, order them to stand and watch you singlehandedly take out small groups of sea raiders. If they have to take part in the fighting they should be around tier three to better survive.
4. There are really just a few goods worth trading with. there is a guide in the stickies. Apart from that. Keep your group small to be cheap and fast. Travel around and win tournaments and buy enterprises in every city. You can sustain several hundred top tier troops with that kind of income.
5. As no faction is best in all groups, it's advisable to hire different faction groups if you aim for the perfect setup. You may also stick to just one faction for roleplaying reasons.
6. The Mamelukes are not OP. They are the single outstanding good troop from the Sarranids. I consider the swadian knight superior. My first few playthroughs I had pure swadian troops. However, nowadays I roll around with Nord Huscarls and Vaegir Marksmen. Also a deadly combination against most foes.