There is a choice of free apps that can be used on CarPlay.
The word on the street is that:
Waze is better within the M25 (but do massively configure it to lose all the cartoon characters). It is more likely to find rat runs to save a minute or two.
Google Maps is better elsewhere in the UK and is better integrated with points of interest, which derive from Google central. It is more likely to give less fiddly routes, sticking with main roads, unless that is going to cost more than a minute or two.
Apple Maps is marginally less good for traffic but fits the ecosystem better (for example, texts appear without hiding the map.)
The only thing that I use the integrated nav for is to estimate arrival range, but I haven't used it enough to know whether it is accurate.