It is hard to say how night EMH will be - sometimes it can be busy if more people take advantage, and sometimes it clears out as non EMH people leave. We like to do am EMH because generally less people like to get up and be there early than those who are willing to stay late, and since it is the start of the day, no one else has entered the park. We have found for the best chance to ride TSMM(our fave!) at least twice, we arrive at RD(or do Am EMH) to do it first thing when it is the shortest line, and then FP it to do again later. It is always a long wait all day, and may have shorter line during EMH, but is generally never a walk-on. They are supposed to be opening a third track, which hopefully will help, but I 'm not sure how soon. The other strategy is to hop in line close to closing, and sometimes lines are shorter than what is showing, and you will get on as long as you are there prior to closing. If you wanted to arrive at opening, you could get a lot done in the morning, leave for a break for a few hrs. and come back to do more later, with getting most must-dos done in the morning, so then can just do what is shorter lines later, and hopefully ride TSMM more times late.
If you want to start the park later, or hop from another park you could make FP for later in the day, and then stay late and hope to do more TSMM! Not sure if you have made FP already, but if not, they are tiered at HS, so you can make one from Tier 1, which would be TSMM for you, and two from Tier 2, which could include Star Tours and IJ (you will not need one for Muppets and GMR is a Tier 1 I believe). They have changed the Animation Academy into the Launch Bay which has Star Wars memorabilia, a short film, and meet and greets with Chewy and Kylo Ren(not sure if meets are available during EMH, so you may need to do those earlier - Good to do in the a.m. if you are there). I think they are also starting a Star Wars stage show that will shown during the day, and are having a Galactic Fireworks at nt. HTH!