I put together several different wikis a long time ago that are helpful if you spend the time with them
https://scanlines.xyz/t/how-to-capture-video-wiki-stand-alone-or-otherwise/
https://scanlines.xyz/t/hardware-video-converters-scalers/
https://scanlines.xyz/t/analog-video-basics-wiki/
it sounds like you are trying to record a composite output from your gear…
are you going to want to monitor on the CRT as well as record at the same time?
you’d need a composite distribution amplifier for that
it sounds like you are looking at the elgato h60s…
it only accepts HDMI inputs so you would need a scaler if you intend on capture in 1080 or 4k.
Remember scalers aren’t magic even if you DID spend a lot of money going from SD > 4K is going to be pretty rough. Even if you did offline scaling via something like topaz labs.
it sounds like you want the best capture device but don’t want to spend the money…
there is no answer for this as there is no stated budget
a capture card simply takes video information via HDMI, composite, component, SDI etc… and sends it to the computer over USB or thunderbolt there isn’t too much to understand however you need to make sure your capture card can accept the resolution/frame rate you are sending it to capture. If you aren’t willing to read manuals and check specs you are going to have a hard time.
lots of questions you’ll need to answer before anyone other than yourself can help much more.
my main capture setup uses
ESG > BMD analog to SDI > BMD ultrastudio HD mini > hyperdeck shuttle 2 via SDI
BMD ultrastudio HD mini > computer via thunderbolt
BMD ultrastudio HD mini > monitor via HDMI out
this allow live monitor, SSD recording, and a HQ stream into the computer all at once.
This is also only about half of the capture rig. I’ve got 2 VHS decks (one for recording, one for SVHS recording), an AV>USB SD card recorder, and a HDMI > USB. This means at any time I could be recording in up to 6 different ways. There are reasons to use all of them and reasons to not use them it becomes a choice rather than the only option at a certain point.
here is plenty more reading I put together about the subject of putting together a system. There is a TON of information here in particular.It also probably reuses some of the links above