... I'm always puzzled by that type of a query ; both links you posted are currently live/valid, so, with respect, why can't you test yourself? Why do others have to test them for you?
In any case, both extensions (not plugins, BTW) belong to a "hybrid" type of an extension, in reality a WebExtension format inside a JetPack extension format; you can see for yourself, if you open the XPIs with 7-zip; as such, they may install under NM28, but they WON'T function as expected (e.g., there's no way to even access their toolbar buttons) ...
I haven't tested with latest St52/St55, but they would install there and SHOULD work as expected ; from past recollection, Browsec only offers 4 free/anonymous nodes; unsure what the current state of Windscribe would be; many years ago already, they had disabled the "anonymous" free tier option (initially 2GB, then just 1GB of monthly traffic was allocated to a fresh extension install), now all versions of their extension require you to register an account with them; a valid/verified e-mail address will grant you 10GB of monthly traffic, on a limited subset of their nodes; but v0.1.61, being an ancient one, might've been blocked from connecting to their servers ...
PS: Please, don't confuse the official upstream apps with the roytam1 forks; use the terms New Moon 28 and Serpent 52 (55) for the latter; FYI, official Basilisk does not support WebExtensions...