Ds2 is only 12 weeks but I have no idea when his feeds settled down, I just went with it. He now feeds every 3 hours during the day and every 4 hours at night, and has done for at least 6 weeks.
I feed from the right breast first most feeds as he seems to prefer that side and it's always produced more milk, if I don't think he's finished I offer him the same side again and finish with the other side. Tbh I have found that for me it doesn't matter if i don't alternate every time, i soon know if one hasn't been used for a couple of feeds!
You don't have to express, ds2 has had a combination of breastfeeding, expressed breastmilk from a bottle, and aptimil formula since birth. He has had about 5 formula feeds in his 12 weeks and it hasn't messed up my supply at all. Maybe best to give it a few weeks for supply to settle down, but ds2 had some aptimil at about 4 weeks.
I only use the standard feeding position in front, but he's a big lad so I have him sat on my knee to feed! I used the Rugby ball hold with ds1 but haven't needed/wanted it this time