I am about ready to rent a gas powered concrete saw (walk behind) so
that I can start the process of installing an interior French drain.

How deep or what fraction of the concrete slab should I cut?

If I go deeper the job of cutting will take longer but I'm guessing the
breakup of the concrete will go faster (will rent concrete breaker).

Is there good reason not to cut all the way through? Would the new
concrete "key" better if some of the old concrete slab juncture is
broken and not sawed smooth?

Basement has a perimeter of 150 feet, will do all of it. Which concrete
breaker would you rent.

65 pound electric breaker for 83.95/day

185 CFM diesel powered air compressor with choice of 30, 60, or 80
pound breaker for 154.95/day

Thank you for any advice.