Anonymous41 I want VIP members to be able to view only VIP topics
Hmmm.. it can be separate Flarum instance for only VIP with only VIP topics. In all other scenario luceos was right, but your VIP will be see a regular topics also (not only VIP topics).
Maybe you can combine https://discuss.flarum.org/d/18158-friendsofflarum-default-group and create some regular group and regular tag for regular users and VIP group and VIP tag for VIPs with cross-excepted permissions. You need to try (I use same model and its work just like a charm). In fact you will be have a two separate independent private groups and VIP members will be able to see only VIP topics after assigning to VIP group and excluding from regular group.
Some common public part with rules/terms/etc still possible.