Matchmaking should be done by both ELO AND WIN RATE, inconsidering the ELO system has been FIXED

The devs recently changed the calculations, but they still arent perfect and they still cleaned up the mess of the previous calculation.

Elo was inflated in the previous calculation. As result the average moved slowly upwards. It started by 1000 elo (which is also the startin elo for that reason), but slowly increased to about 1500-1600 as a bug in the calculation.

Now the made a fix, so the system isnt inflated anymore, but there are still other exploits (mainly with smurf accounts). Also this fix will stop the inflated, but they mess of the previous calculation is still present. The devs can improve their formula, but if they wont clean up their mess, nothing will really help to improve the situation.

For more info about all these issues of the past, see Analyses of the ratings - Spotting the issues.

That being said, let us have a look at your suggestions.

New players dont really understand what to pick, smurfs will probably pick the lowest, so they can smurf even more. I dont see any benefits from this. I also have no idea this will improve the match making. You will gain or lose already more elo in you first games. So your elo will be adjusted quickly after the first games, no matter what you pick. I have no real hope that picking a rating at the start will help at all.

Inflation on the ladder is really messing up this one. Normally you start at average player on the ladder and you will move up or down based on your first games. But due to the inflation you start at 1000 elo, which is about bottom 5% or something like that. As result you have to climb over 45% of the ladder before you are at the normal starting point. This is one of the reason why just fixing the calculation isnt the solution. The devs really need to clean the ladder.

I can see improvements in how much elo you win if you are on a winning streak. In the thread that is already mentioned earlier (Analyses of the ratings - Spotting the issues) i also suggests using TrueSkill or Glicko-2 as rating system over Elo. It looks to me these systems will improve the rate to catch up. They look more flexible systems.

Winrate shouldnt matter. Match making will make sure that everyone will be around 50%, if it functions well. Only exceptions are really the real top and bottom of a ladder. These high winrates are the result of the mess of the past. This is again a reason why i think the devs need to clean up the mess at the TG ladder. I would even go that far as just resetting the full TG ladder.