We tend to use slower burning powders in many cartridges than handloaders of a previous generation. In Europe, N140 was the norm in 308 for 150-175gn bullets for many, many years - and is still 'the norm' for many in the UK today. It is in fact, not a particularly 'fast burning' powder for the cartridge. For some reason, Viht's maximum N140 loads are much lower than they used to be, and are in practice so low that they are verging on being 'starting' rather than 'maximum'. European 308 Win shooters have long exceeded factory maximum charge weights - and by a lot at that - even when loading for very short freebore chambers. ie 155gn bullets in Palma 95, Bisley 150 and similar. Factory Remington 700 VS, Police, SPS Varmint etc chambers allow still higher N140 charges.
N150 is common here for bullets heavier than 175gn, and to be honest I've preferred this one for 155gn class handloads too, although MVs are often a bit down.
Going back to the wider question, 308 Win is an exceptionally flexible, 'well balanced' cartridge making it very propellant tolerant. That is because the case capacity matches the bore size very well, and as Bryan Litz has long argued, 150-175gn weight bullets are on the light side for .30-calibre, not 'normal weight' at all. Go back to Ken Waters' 'Pet loads' for the 308 win, the massive 'Update' version of his 308 handloading articles originally published in July 1979 in 'Handloader' Magazine, and you find many propellants that will surprise modern users of the cartridge.
To take 165/168gn bullets, we have (recommended) loads for IMR-3031, WW-748, H322, H4895, IMR-4895, WW-760, IMR-4064, N202, IMR-4320.
180/190gn bullets have all those plus Hodgdon H335 and BL-C(2), also Norma MRP (!), IMR-4831, and WW-785 - a much wider burning rate range than most would consider nowadays. In particular, surprising to modern 'eyes' is the use of Hodgdon H322 (this would be the Scottish ICI Nobel manufactured version then, but today's Australian ADI made stuff won't be very different) and IMR-3031, both regarded as FAR too fast burning for this combination. Yet, the MVs are perfectly respectable - high even for 3031 - and accuracy was regarded as superior with match bullets. I've often thought IMR-3031 an underrated powder in this role and suspect the 'problem' with it hasn't been one of performance rather it being 'old-fashioned' and also poorly suited to mechanical powder measures with its long grain kernels. The relatively fast burning Norma N202 (same thing as Alliant Re15) produced the most accurate overall number of several score combinations under the old 190gn Winchester BT, 40.0gn for 2,361 fps from a 24-inch barrel Winchester Model 70 Target at what was described as 'moderate' pressures. H322 was regarded as an excellent choice for shorter distance match loads, and was also used in the larger case 30-06 in that role by many bolt-rifle shooters in those days. (Too fast burning for the M1 and M14/M1A semi-auto rifle mechanisms where 4064/4895 was the standard.)
KW didn't have any Viht grades in his tests as the marque wasn't being imported into the US in the mid/late 70s.
A final thought on Viht burning rates in the cartridge is that N135, considerably faster burning than N140, is the canister version of Viht's standard powder for 7.62X51mm NATO ball ammunition with 146-150gn FMJBT bullets.
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