NEC 2020 Compliant feed to an outbuilding

I am doing something similar to Running Service to Outbuilding. I tried asking for clarification there, but couldn’t figure out how to. Sorry to start a new Q. If there is a better way, I’d appreciate feedback for the future. Also, FYI, this is asking for details related to a broader question I asked (400 Amp service to 225 amp and 150 amp panels). Hopefully, the below reflects what I learned there 🙂

I have a 2 car detached garage in Washington state, across a dirt county road from the main house (50-75 feet – need to measure). I want a 70 amp feeder to it (50 amp 240v car charger, 2 garage door openers, well pump, lights, GP receptacles). I’ve tried to plan the best I could based on the previous post and reading NEC 2020. I’d appreciate feedback on my plans, detailed below.

I believe I need a disconnect at the garage, so I’m planning a panel with a 70A main breaker, and 3 breakers for 3 branch circuits. E.g., Eaton BRP10B100, BR270, BR250, BRP115A1CS, and BR120. I don’t also need a disconnect on the outside of the garage, do I?

I plan on running wires from the main house in a 1" PVC conduit in a trench 20" deep with 2" of sand, then the conduit, then sand, then dirt back to grade. I plan on using 3 wires of 4 AWG AL XHHW-2 and one 8 AWG solid copper wire. I believe I also need an 8 AWG solid copper wire to a copper grounding rod at the garage.

Similar to the $3K+ 400 AMP Meter Combo on the other question, I plan on using a much less expensive version, the Siemens MC0816B1400RLTM. The description of this says "This 400 Amp meter-load center combination is provided with one 200 Amp main breaker that feeds an 8 space, 16 circuit interior with feed-thru lugs that can be used to feed a load center down stream." Does that mean I can add lugs downstream of the 200A breaker and have my feeder wires connected there? Or do I first need another 70A breaker installed after the 200A breaker and before the feeder wires?