I'd say no need to still also install VST2 versions (as VST3 is 'in charge' now for like 10 years or so and Steinberg is trying hard to kill VST2 anyway, so most plugin devs should have ironed out the VST3 versions by now I'd think).
Unless you have older projects done with VST2 version, but then you'd notice when you try to open them and can still install the missing VST2 versions.
I'd say no need to still also install VST2 versions (as VST3 is 'in charge' now for like 10 years or so and Steinberg is trying hard to kill VST2 anyway, so most plugin devs should have ironed out the VST3 versions by now I'd think).
Unless you have older projects done with VST2 version, but then you'd notice when you try to open them and can still install the missing VST2 versions.
That's one school of thought. Another would say install both VST and vst3 versions for troubleshooting purposes. You're probably fine either way.
Hopefully you will also have another choice to get confused by soon. Hopefully you will have the option of CLAP plugins. Most likely a superior format.