What bitrate for upscaling VHS or camcorder video?

Wondering what bitrate is ideal for upscaling old standard definition video. If I leave it on auto, it uses a very high bitrate of around 90 Mb/s, which far exceeds the need for low resolution video like this, so I was setting it at 40 Mb/s. Is that still way too high? I mean, I know there is no harm, but if I can reduce the file size without effectively losing quality for old video upscaling, it’s nice to be able to do that.

it really depends. there is no straight answer. depends how much motion the movie has, what background, etc.
what i do, not to get mixed up, I export it at the highest bitrate available (x264 180/Mbps), then load the output file to Handbrake, encoding it using x265 with CRF settings that i found works the best for me.
23 is a good default for x264, and 28 is the default for x265. 18 for x264 or 24 for x265, should be visually transparent; anything lower will probably just waste file size.
Values of ±6 will result in about half / twice the filesize.