In general, usage is totally OK for international travel.
It depends on your type of travel and destinations - there are places in the world where it is hard to get reasonable prices by any OBT. For the rest, a suitable config of the provider and class settings will do.
Especially on reseller systems, you will be in conflict with the reseller's templates, as they will not do any config you like.
In any case, a reasonable restriction will be to have connecting flights with more than one stop excluded from self booking. Most probably, your travel agent will find better prices or connections here.