maybe i can offer some usefull information about rhinelanders
i bred them for about 3 or 4 years.
all 3 coat colors (self/sport, broken/standard, and charlies) can be used in breeding.
not this comes from an american breeder, i was not terribly familure with non-american bred rhinelanders.
for the most part self/sport have heavier bone, they tend to be stockier animals
and charlies have considerably lighter bone, they tend to be more hare-looking.
when i bred, i always judged what animals i kept and used in my breeding program based on my standard/broken animals.
for instance, i might have a standard/broken doe that has great markings but maybe is a little stockier then i wanted, i would try to breed her to either a light boned standard/broken or a charlie.
it also helps clean up muddy side markings to use charlies. i found that many breeders might have great type but the side markings are muddy and sloppy looking.
now this is completely by choice, i didn't have an issue with rehoming unwanted babies so i didn't do it, butmany breeders cull out of the box. they take everything that isn't standard/broken and cull at day 1.
i started off with only a pair or 2 standard/broken rhines. the buck had great type but muddy side patterns, and the doe had great side markings but not as great type and spine markings.
my advice would be to try to get a trio at least. i would honestly suggest if you really want to breed them and can afford to do so to get 2 bucks and 3 does. that gives you some playing around with. i always will suggest to look for the best buck and take the best (but maybe not as good) doe(s). to not just look at the markings on the animals (if they are selfs, brokens, or charlies) but go for the body type.
and enjoy them, rhinelanders are a great breed, they are active and fun, but not as 'wild' as many high-arch breeds can be.
anyway, i hope i helped, feels like i was just kinda talking random about the breed lol and good luck!