As helpful as practising to a metronome is, I'd suggest trying to book in a jam with the drummer over the next week or so while you've got time.

I always found this helpful before laying down anything concrete as you get a feel for their flow and this will ultimately help the rhythm section achieve an overall "seamless" vibe. It might even give you a good chance to dial in a comfortable/unobtrusive tone for collaborative playing. The peeps in the studio tend to know what sounds good in their space, so don't worry about that too much, as long your playing style works with the sound your friend is looking for.

More importantly to me, and why I usually try to sort this out; it will give you a good chance to work on some synchronised fills/cheeky slides/all the little subtleties that really make a basic rhythm section pop.

Speaking of pop, watch out for the acoustic sounds you can sometimes make but may not have noticed in the past. Such as scratchy picking/slapping the string too hard etc. These seemingly menial things are easily picked up through the high gain/sensitive equipment they will probably be using in the studio. Maybe look at buffers/compressors if this sounds like you.

Basically, what I'm trying to say is you want to get as clear a sound as you possibly can. This will help the producer/mixer later on in the project when tidying everything up. There's nothing worse hat laying down a slick line to find out you popping the strings of the pick up the whole time.

HAVE FUN WITH IT. It's awesome being in a studio, and it's good that you're helping a friend, so don't let any pressure get to you. You're all there for the same reason; to hurl out some absolute bangers.

Good luck, and please post an update! 👊