Wait, let's back up a second here...
First off ... <sigh> ... why do people capture VHS to the wrong format (H.264), in the wrong container (MKV), with the wrong program (OBS). I just do not understand this. I can only guess folks have been led astray by others that equally have no idea how to properly capture analog videotapes. H.264 is a delivery/final format, not capture format. OBS is primarily a streaming capture tool, with analog being a (semi-functional) afterthought feature.
We capture VHS in
VirtualDub to
Huffyuv for a reason.
Handbrake is awful when it comes to aspect ratios, probably literally the single worst problem it has. The software is really stupid when it comes to AR, both in reading the source files, and especially on a resize. It's equally quite terrible at framerates. It was, and still is, primarily a program used to convert a disc (DVD/Blu-ray) to MKV/MP4.
So the underlying problem here is with the entire method, and choice of software. The AR is fubar because the method/software is fubar.