You said that an aperture (for example f8) in small format is not the same as that aperture (f8) in large format.
I know what I said, and I know what you said. My formulation was ironic, but you took it literally. Can't blame you for that.
What you likely meant is that, in practice, one will tend to stop down the lens on a large format camera more that one would a small or medium format camera.
Yes, thank you for correcting me. That is indeed what I meant. I will try to formulate as accurately as possible in the future.
Again, not sure where you intended to go with this diversion, but I remain with the position that the larger the format, the more light you need.
I should have mentioned that I'd prefer continuous lights, I don't need all the bells and whistles (can do without remote control), and am using a variety of cameras from 35mm to 8x10 / 11x14 large format. Something really basic would do. Heck, I'd use something from the 30s...
I personally find/found continuous light with larger formats such as 8x10 annoying and just not worth it. With modern LED lights, you have to resort to pretty high-powered (and expensive) setups to get enough light to begin with. With old tungsten / halogen lights, the amount of heat you'll produce gets problematic really fast, not to mention that any wrong movement and you burn your elbow etc. Stuff really gets hot! Count on needing several kilowatts of tungsten light to make a portrait on 8x10 without compromising the heck out of everything.
LED will still take >200W (actual power, not 'tungsten equivalent'!) per head, and that's the very bare minimum. Forget about the cheap entry-level kits with two 60W LED bulbs. Those will get you absolutely nowhere with 4x5, let alone larger. Powerful LED heads are costly, and will have noisy fans running all the time (although strobe heads can have those, too). I honestly would only go for LED if you need to do video.
You'd have to look up prices currently, but I think your best value will still be basic strobe kit with two heads and some modifiers and heads in the 400Ws - 600Ws range, depending on your budget. Kits like these generally come with one or two softboxes, perhaps a set of barndoors, maybe a grid or something and a pair of stands to put the heads on. That's all you need to get started and you can have lots of fun with a setup like that. If shopping for new stuff, check out 'newer' brands like Godox and FalconEyes (although they've been around for decades now, too). They offer nice kits for reasonable money. Check the second hand market as well; some photographers are dumping their strobes because they want to migrate to LED for video purposes.
If you can, see if you can find someone near you with some studio equipment. Doesn't matter if it's high end or entry level, if it's continuous or strobe. Just to get a feeling for what it does and what you might need.
20W LED bulbs? That's nice if you're shooting digital and can work at ISO 400 and higher all the time. Forget it for film shoots.