I haven't done much rigid in a while & avoided it where possible. It is a hassle to bend and thread. I love it for underground, as I can bury it 6 inches deep. Much less digging and it won't get damaged.
Standard Raco type boxes, 4 inch and 4 11/16 are usually on shelf with KO's up to 1 inch and maybe larger. These boxes are usually cheaper than 6x6 or larger that have no KO's. Cutting KO's kills a lot of time. Use them only when you need larger space. Keep a few compression fittings on hand and maybe a few Ericsons but keep them locked up and hand out as needed. They are costly in small sizes and highway robbery in larger sizes. Threading eqpmt is already on job, I'm sure, so use locknuts and bushings wherever possible. Sealing locknuts are good for some damp locations, Myers hubs for more severe locations. Cast iron FS boxes are available with lots of different hubs and are good for exposure to physical damage. Again, these are costly, last I remember. But they are good for pedestal apps, like a 1 inch RMC pedestal to 1 side of hub and 1 inch RMC raceway into other side. I saw these used a lot where we anchored to flooring molds and they were poured in concrete.
Others here make a good point. You really should get some field experience. Nothing like it. You will get firsthand knowledge of how usable a product is in tight spaces, dim light, no special tools nearby, time pressure on you, etc. We had a guy working with us one summer, an electrical engineering student. He was a tiny guy, about 5 feet tall, 90 pounds. He got a lot of crap jobs, walking ceilings, under platforms, etc. He said when leaving that he learned more that summer than he ever had in class up to that point. I think he'd finished 1st year college, maybe 2nd.
Ask your boss to let you work some nights & Saturdays with a crew. Be a helper to a seasoned electrician. Swallow your pride and don't be afraid to get dirty. You will learn a lot and the guys you work with will respect you no end for doing it. They may ride you awhile, as often happens with newbies, but it will fade away. You may also be able to teach them something about estimating, planning and cost control. Some of them may have no idea how much anything costs. Everyone should get a chance to see things from the other end.