1. When do you guys think Ether will move to POS? Is it by the end of the year?
The newest estimate is Q4 2022. The lead PoS developer predicted that PoS would be deployed in Q3 2022 at the earliest. So yes, I would guess before the end of the year. However, PoS was supposed to happen back in 2016-2017. Miners panicked back then. But it has been delayed over & over again. So don't be surprised if the new estimate is 2023.
2. Are miners still buying RTX GPUs today? If so, are they only buying the 3090s with no LHR?
It seems to be that most medium-size GPU mining farms (50-500 cards) buy mid-range video cards like RX 5700's, RTX 3070's or RX 6700 XT's. However, the best investment is probably the RTX 3060L 12GB. Just dual mine ETH+CFX to get 45 Mh total. I have a rig of them and it has been my most profitable rig.
Of course, most n00b miners only buy equipment during a gold rush for inflated prices. I was dumb enough to open an ETH warehouse in early 2018. I bulk ordered RX 570 cards for $370 each. When ETH price crashed, profit didn't cover the rent. I defaulted on my lease and the business went bankrupt. I had to sell the cards for $90 at the end of 2018. Whoever bought those cards has made 3-5x their investment back.
The wisest time to buy video cards is right after the ETH PoS crash. The only problem, though, is you probably won't make any profit for a few years. Just HODL the coins, then when the next bull run happens; sell all your coins as well as the GPUs. This is exactly what I did during 2019-2021, and I made a killing. I bought GTX 1060's for $140, made $400 of mining profit, then sold them for $330.
3. Also on LHR, I know there are several software that claim they can unblock it and get back 70% of its power. But realistically how true is this?
70% is the average, although the actual unlock range can be 60-80%. I recommend dual mining on LHR units since you can attain 90%-95% the profit on the FHR version. Set the power limit to 70-80%.