300W isn't overkill for a 2'x4' imo, but get these instead of what you linked..

Or if you can find a used 240W Quantum Board, then you can dim it too fit your plants needs.

I started with CFLs years back, then bought a 300 actual watt burple, then build my own with quality led strips, then bought this Quantum Board. I'll be buying another when I need more light/ have more space.

Yep! Mounting them vertically 1 light per row would be best.

I've seen set ups that pivot down in a hinge, so you can raise them to access the plants easier.

If they're all LEDs a good way to oversimplify it is to check the wattage of each light. I'd say those shop lights at around ~40W each are great per row.

I have a similar setup and use these ones since you can plug one into the next.

I agree with this as well. I ended up getting something similar and went back and bought another set. Extremely easy to install. General rule of thumb on lighting is you want to spread your wattage out to as many different light sources as possible. It's a game changer in the garage.

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https://www.amazon.com/gp/product/B07TM97LWY/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

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That's what I got. Easy to mount either via chain or clips