The stroke trajectory is something that I'll try out for sure.While it has limitations as a tool, try to use your swing trajectory as a guide for the ball. In broad terms, the shape of your stroke should guide the ball and also be used to adjust to the incoming spin.
As an upright player, I can speak about the value of being upright vs getting lower. The main value is being able to start below the ball for most strokes in order to get decent topspin. Because I have long arms, I can get away with being a bit more upright than I should be. However, nothing in life is free - when you are lower, your swing trajectories can have a more natural forward component than they would when you are upright, where more of your momentum will be upwards. That said, you can compensate for the swing planes. But you have to be aware of the tradeoffs because even as upright as I usually play, I sometimes have to get lower for service return and third balls against a certain kind/level of player as I can't generate the quality I need to against their ball trajectories or spin quality without it.
The benefits of being low noted, I point this out because I see many players beating themselves up over playing upright, but not realizing that a lot of it can be compensated by adjusting your swing trajectory if you have the right mindset. And to me, many people who start learning later, especially with some of the issues you can get trying to stay low, should just learn to compensated with reasonable swing trajectories so that they don't find playing table tennis too painful. But to each his own, just need to help people be aware that you can play decent table tennis without being low all the time, though there are limits on what you can do with low balls when you are not now relative to the table.
Amazingly, my legs aren't as nearly as sore as my back, but having my technique being based on staying low is something that's in the back of my mind as I get older.