Mike,
The old thinking was to get every level player (by tee shot distance, usually with tees at 290, 260, 230, 200, maybe 170 and 140, approximate) to the same LZ so they all had the same strategy and hazards to negotiate. However, that left the 140 hitter with two shots to the green, and the 290 driver with a short iron, etc.
New thinking is proportional distance, with tees about 90, 80, 70, and 60% of back tees. If based strictly on the mid point of varying levels of drives, it would be some odd numbers, like 92%, 84%, etc. with the forward tees at less than 50% (I.e. based on 140 yards vs 290-300 yards) While perfect in theory, I am not sure we have to get everyone hitting exactly the same club by proportionate distance.
BTW, I establish the mid point based on the few driving distance studies out there, and it is amazing that golfers hit drivers all distance, but there are little clusters at those distances, so they 230 drive centers on a class of player who really hits from 220-240, etc.
However, that does tend to spread the need for strategic hazards down the fairway. The question is whether it is worth investing in sand bunkers for some of the little used (in theory) portions of the fairway, and on the flip side, if it is desirable to have hazards at distances to challenge the 140 and 170 hitters, who have enough problems to negotiate.
I go back and forth on how many tees. Again, in theory, you nearly capture everyone at a good playing length with six sets of tees. In practice, the pro shop prefers no more than 5, and many prefer 4. If a course tops out less than 7K, 4 is probably enough.