I u8sed to ;live in Chi & also Pagham too. Traffic around Chi is grid locked quite often these days. The main ‘benefit’ of Chi is to live inside the walls per se. Then you dont have to drive and you can enjoy the city. This is expensive. If you live outside, you can spend ages trying to get inside if you see what I mean.
Road riding, excellent
MTB, better in the winter IMHO as the ‘deer trails’ are easier to find. Otherwise you tend to get lumbered with the SDW. Though Queen Elizabeth Country Park isn’t far and is a giggle
Track riding you have Portsmouth track and Calshott Spit
Having been MTBing around the Hebden Bridge area, Id always aim for the Peak side of Sheffield if it were me
If you do move to Chichester, ping me a message and Ill gladly pass on details of some local cyclists who would be happy to ride with you on or off road