I had it on my phone, in the newest Vivaldi 8.2 rebranding where they now support extensions and it runs a lot better than any previous version and... also for me, it surpasses most browsers..
I use a S23 Ultra and is beautiful, so dunno where the idea that it causes lag in chromium based browsers
as for ff well... no offense but it barely keeps up on Windows platforms, it performs at its best on Linux, but other platforms currently do not allow the same power across the device segments.
tho i must say, back when I used to have a Samsung A50, it did a bit better but this is a vague memory, again.
as for me, I do not use Ghostery on my phone at all, I mainly have a system wide AdBlocking+AdGuard Home and it does suffice my needs.
i also use a remote based protection from Sophos and that's pretty much it.
tl:dr : ghostery lag in ff can come from both. ghostery in chromium browsers, rare to very infrequent. bugs in newer versions... possible and that's the reason they got a GitHub where you can tell them and maybe some can do a pull request? or somethin between the lines.. it gets fixed, eventually.
new browser versions lags a bit more, or older vs newer being a bit more consistent, entirely possible. One word, subjective