i have solid and broken choc mini rexes. i can answer part of that from what info i have read or from my first breeding.
Chocolate and Lilac can be bred together as Lilac is the dilute of Chocolate. Chocolate may also be bred to Black or to Blue. If they must be bred into the agouti group, then Lynx would be the only choice. Breeding to Castors will result in Castors with incorrect ear lacing and top color.
Chocolate: Best bred to black, blue, chocolate, lilac. Use caution when breeding to lynx (can result in poor lynx and the unshowable chocolate castor, but both chocolate and chocolate castor can be useful in a lynx breeding program, if that is your aim), opals (can again result in poor lynx and chocolate castors), and red (can result in poor reds and unshowable chocolate castors, but some breeders breed chocolate into red in order to hide the undesirable smut...the chocolate coloured smut hides easier in the red coat than black coloured smut would). Avoid breeding to californian, chinchilla, sable, and seal as it can result in unshowable colours.
choc x choc should produce all choc i think or at least most of the litter if the parents are not hiding unwanted genes. i'm still learning the genetic part not sure if reccesive or dominant on that color never checked on it.
we don't have choc bucks so before i found info above this is what we did- we bred a castor to a broken choc her litter came out broken choc, broken castor and solids of both also. we bred a choc to a tort and had brokens and solids of different colors but we lost the babies from being cold on wire. most of hers were broken and solid brown and black colors and one or 2 white ones when born.
hopefully someone else with better genetic knowledge can come along and help u more but maybe this info will at least help u to try to answer ur questions till someone else comes along to help ya.