It would be hard to have too much oil to the camshaft. The raised oil modification to the timing case was not invented for no reason, and it is not taking oil supply from elsewhere. But I do think that there would be enough oil to the cams when pressure fed rocker oiling is used. The reduced oil supply to the rockers when fed from the return line was a fad that was common in the era that Ariel did it. The main reason for reducing oil to the rockers was to help prevent over oiling of valve guides. Today, valve guide oil seals are used universally and top end oiling is always under pressure. I have the raised timing case oil level on all my singles except a 49VH.
At low revs there is no problem with a flooded bearing. However, as the speeds increase, oil whirl becomes a problem. Oil whirl is very undesirable because it introduces cyclic rhythms and vibrations. The cyclic stresses are imposed on the shaft, bearings and machine. Hydraulic pressure within the bearing cage due to increasing revs can split the brass cage that hold the balls in position, the balls move together, the outer ring moves in relation to the inner and the balls fall out of the tracks. There are however bearings that are designed for flooded applications, but they are a specialist bearing.
If you look inside your Burman gearbox you will see that the casing is very tight around the bearings so as to exclude too much oil or grease from the bearing and prevent flooded application. In the BA, the ks end mainshaft bearing even has a metal shield to the outer face so as to minimise the grease in the bearing. And the mainshaft bearings are not flooded unless the gearbox is over full. But I can imagine the gears would really flick the oil/grease about.I do however always pack the bearing with grease initially as it may run dry for a while otherwise.