This all on same breaker. Left, spliced wires are hot, but do nothing and there's no switch for them.
Wires on the right are on a switch that controls two other lights closer to the breaker.
Can I just removed the splice and terminate the hot wires into a box mounted on the rafter?
i think the spliced goes to these wires, then leads somewhere else?
I agree with using the Wagos, as they are the best thing ever for tying wires together. Get a bunch of 2 and 3 holes, and a 25 pack of five holes. Grounds need to be continuous so they get pigtailed to the fixture under the green screw, and under the box screw if you use a metal box, which I generally use in ceilings. If your box is metal and doesn't have a ground screw, they sell them at the hardware store as well.
I would argue that a splice should always be in a box or within a rated fixture to keep home inspectors and code inspectors happy. Boxes must be accessible. Your local Authority Having Jurisdiction may allow them to be behind a drop ceiling, but you cannot drywall over them without cutting a hole and adding a blank plate.
If you're joining to existing, it looks like you'll need 12 awg as mentioned above. If pulling all new you can use 14 awg since led fixtures are unlikely to ever pull 15 amps, though I rewired the outlets and fixtures in my garage with all 12 awg for future proofing and would recommend the same. You can put a 15A breaker on 12 awg but not a 20A on 14 awg.
For wire made since around 2001, yellow is 12 awg and white is 14 awg. For wire before that, you need to read the jacket.
I forgot to add, and don't feel like editing, always buy the 250 foot rolls when you buy wire because the cost is not that much more overall and you'll have wire left over for the next thing you find.