CC compared to DP

They are pretty close so if u have other Pokémon that need TMs I'd use them elsewhere. However, if u don't have many priorities, wait until you have 2 charged TMs. That way, if u don't get DP, you can reroll again and will get either DP or CC.

I always look at damage per energy first

DP: 90/50
CP 100/100

Then I look at Time to use the same amount of energy, in this case 100
DP: 2.7 Sec * 2 = 5.4
CP: 2.3 Seconds

Then I look at which is faster and decide how many quick moves can I get in that 3.1 seconds

It's 3.5 Counters. I tend to round down for 100 because I waste more at end. So 36 Damage and 24 Energy.

Then I compare.
2 DPs = 180 Damage for 100 Energy = 1.78
1 CC = 136 Damage for 76 Energy = 1.78

Now most sites have CC at about 95% of DP, which looks pretty good to me when you factor in the Energy Bar is 100 so it is more likely to suffer from wasted energy

I wouldn't recommend using TMs on CC any more than I would on Hurricane.

DP all the way!

C/CL is very close in DPS to C/DP, about 95% effectiveness if spamming non stop. If you dodge all moves it's even closer.

I am only speculating here but I think C/DP isn't rated A only because it does the most DPS, but also for other reasons - since it only requires 50 energy there's less overkill / energy wastage and it's still decently fast, not amazing but it's only 0.4s slower than Close Combat, so you can still dodge against slower quick moves

Whereas other moveset comparisons, you might be trading dodgability for DPS e.g. Overheat vs Flamethrower on Flareon, so an 'A' rated moveset might not be better depending on playstyle, but on Machamp, C/DP doesn't have any significant downsides, hence why it's A and the rest aren't.

C/CL is close enough in effectiveness that it's not worth using a TM in my opinion unless you're doing several raids a day and you're drowning in TMs.

I would rather save that TM for another Machamp evolve or if you get one from a raid, because one Machamp is not enough for high level raids, and most likely Machamp is going to be the most valued attacker with nerfs to generalist attackers that deal neutral damage with STAB, such as Dragonite and Tyranitar and buffs to super effectiveness, you now have even more reason to have at least one good Machamp, for example against Snorlax, Lapras and Tyranitar raid bosses, but to be honest the best lineup for these raids might be 6 Machamps, so that's what you should save your TMs for.