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There are two schools of thought about fitting seals to exhaust valve guides. One says the pressure in the exhaust will tend to stop the oil coming down the guide, and therefore don't fit them. In my (limited) experience running 12G1805 heads with bronze exhaust guides if they are not fitted then oil consumption goes up quite a bit when the oil gets hot. When I stripped one head recently without exhaust seals the back of the exhaust valve was well coked up, looked like it was just trickling down the stem and then coking.

With a 1330 I was running a couple of years back there was visible film of oil on the back of the car near the exhaust, but never any signs of oily plugs, again I think it was just going down the exhaust guide and out the back. Side benefit - the RC40 has been on it for over 25 years and still no signs of rusting out...

Why recommend putting the used seals on the exhaust? Bit of a compromise really, as I would like a small amount of oil to reach the exhaust guide rather than having it run dry. I have done this to a head about 6 months back, and results seem good so far. With the next one I may try cutting a very narrow slot in the exhaust stem seal and see how this goes.

Personally, I never put seals on exhaust valve guides, I was taught, many years ago that with the amount of heat in the valve stems, a little extra lubrication was far better than not enough. however that is not the main point, talking of valve guides has reminded me of a head I once bought & when I started to work on it, it was obvious that the guides had been pushed in too far. I think someone assumed the groove for the seals indicated how far to push them in. This might be worth checking.
As regards oil, I use Valvoline Racing 20/50 & blank off the airflow to the cooler in winter.
PCV valves can behave in mysterious ways, I remember in the 60's some competition cars had the valve blanked off & holes cut in the breather pipe leading to it, in order to comply with Gp2 regs without actually using the valve, may have been Abingdon, not sure.