"I thought Twitter Spaces were good, what are their disadvantages?"
Centralization, censorship, data-harvesting, ads, walled garden, cross-device syndication... tons of disadvantages to twitter, yourtube, spotify, etc.

"Can the user of Cast.garden control the resolution of the video they receive in?"
Yes, 100%.

I have the cast.garden site set to 1080, 720, 480, 240, and audio-only options for each post, depending on its media-type. If you really need 144, I can enable that too if there's enough demand for it.