You'll want 50mm spacing for your bridge pickup, neck will be 50mm as standard.
If you want to have a coil split/tap, you'll need an extra 2 switches, one per pickup if you don't want them both tapped at the same time; a push-pull pot on each tone control is the setup I've got on my LP. It's not impossible to do, but when I fitted my Mules, the pots were already there, having been fitted by my local guitar tech when he put a previous Bareknuckle in for me. This also meant I had a correct 4-conductor wiring scheme to copy from. The stock Epi pickups will be 2 conductor, so if you go down the coil tap route, you'll have to install the new pots and figure out the wiring too.
Potted pickups are the standard option as far as I know, but I don't think there's any difference in price between potted and unpotted pickups.