Flyingstone: Thanks. Indeed. FCTM says with FMC 10.7 it is normal; it doesn't say prohibited. That's my point. Plus, FMC 10.8 is now out there. The FCTM does complicate it by mentioning that with FMC 10.8 and arming VNAV for takeoff you normally engage A/P above minimum height. Complicate, because what if you have 10.8 and don't arm VNAV?
I'd always been told that TOGA has a better ratio for acceleration v climb than LVL CHG; that was all. When bugging UP in TOGA the FD gives 0-200fpm ROC. With A/P engaged, not in VNAV, will it be so very different? If you get more climb than acceleration in LVL CHG the only -ve to that is you'll take a little longer to clean up the flaps.
Parkfell: No dual channel operations in my questions.