Blockquote VRChat+ members could unlock exclusive particle effects and animations to enhance their avatars or in-world actions.
all of these can already be done by avatar creators, if they wanted they could add trail renderers particles or better animations.
Custom UI Themes
VRChat+ members could personalise their user interface with custom themes.
this is also already a VRC+ feature it was announced in this dev update
Exclusive Events
this can be done by event organizers however i dont personally see the point in doing this.
Vote on Future Updates: Enable players to prioritise which future updates they’d like to see.
Currently anyone can suggest or vote on features to be added to VRChat using the VRChat canny this probably shouldnt be locked behind VRC+
Exclusive Avatars
im not sure what the point of this would be when anyone can create avatars already
Virtual Pets
im not sure what you mean by this one but based on what you described this also kinda already exists with assets like the among us follower which anyone can put on any avatar they create
Enhanced Voice and Audio Features
all these features also already exist plenty of users use stuff like voice mod to change the way their voice sounds in game.
worlds creators can change the way sounds and voices work in their worlds.
personal audio zones sounds like earmuff mode if im understanding you correctly.
and avatar creators can put custom sound effects on avatars already
Early Access to New Features
VRChat does open betas to help test new features that might come to VRChat Open Beta - VRChat Wiki