I BIAB and do sort of a sparge. I mash with somewhere between 1.25-1.5qts of water per pound of grain. I get a second pot of water, usually 1/2 as much as is in the mash, to 170F. When the mash is done, I pull the grain sack out and let it drain. Then, I dunk the sack in the second pot with the sparge (if you want to call it that) water and let it sit for 10min. I then combine the 2 pots of wort into one and boil. The system works well for me. I’m consistently between about 72-78% eff. Sometimes even higher.
And yes, you can BIAB any recipe you want. Your only limitation is how much grain your pot/sack can handle. I’ve mashed up to 13lbs. Anything over that and I have to compensate with some extract in the boil. Or if I’m making a real big beer like some sort of Imperial or Barley Wine, I just brew a 3 or 4gal batch.