My general rule is that you should plan 1RU of air flow around each piece of equipment in the rack and plan for exhaust from whatever space you put it into. So, if you put the rack into a sealed closet space without exhaust, you may want to put a 2RU fan at the top of the rack to pull the hot air out of the space and the vent panels between the equipment will allow cool air into the space and around the equipment.
https://forums.audioholics.com/forums/threads/so-here-we-go-24-a-v-zones-w-10-sources.83272/
The VT1 panels from Middle Atlantic have a minimal hole pattern design which should be plenty if you use them between all of the equipment.
Each RU is 1.75" tall, so you can typically do the math on the height of the gear. AV receivers fall into the 4 or 5RU category quite often, but most other gear is now under 1RU, like streaming devices. You can pick up plain rack shelves to set equipment on, but if you want it to look nice, then a custom rack shelf with a custom faceplate will really help to make things look nice.
Look through the photos of what I posted above. I have swapped some stuff in the rack, but my audio distribution hasn't been touched in the past 10+ years since I originally posted that thread. The small equipment rack that I show later in the thread is still in place and looks quite similar. That small one backs to a coat closet and while I don't have any active cooling for the closet, the equipment doesn't have any amplifiers and the game systems or Blu-ray Disc player in there hasn't complained... yet. I can just open the door to the coat closet if I wanted to. But, it shows how basic rack rail, screwed to studs, then framed out with some decent looking wood can create a nice looking rack. If I did run into issues with heat with that smaller rack, I could put a 2RU fan at the top and add a few vent panels if I needed to, so that was planned for.
Generally, my rule is to plan for more space and to have it available. I have added a third rack next to my other two in the basement to give me a bit more room, but it is mostly empty at this point. But, my rule remains the same. When possible: 1RU venting above each piece of gear. This will leave you room to access cabling and gear far more easily.