GrapheneOS is significantly different to other ROMs in that it is hardened https://grapheneos.org.
LineageOS is one of the most mainstream ROMs. We only recommend devices with official support as we believe their charter helps ensure some quality control.
A lot of other ROMs really aren’t anything special. They often are based on LineageOS with minor UI changes, and default included applications.
Keep in mind the GlassROM org consists of one person https://github.com/GlassROM. I haven’t personally heard of this ROM before, so I would hazard to guess it’s a fairly small/new project. It appears to be based on LineageOS as most ROMs are.
Trust is always a concern, particularly as Android requires the use of proprietary closed-source blobs, included with the ROM to make devices work. These are usually extracted from stock ROMs.
I would be very careful about what custom ROMs I used.