On adding the plants, there are many differing ideas but for my choice, and I currently had the time/funds, I would go ahead and add them. My tanks are often changing and always under construction in some way. If plants are not doing well, I'm changing them in some way. If they are doing well and growing, they need trimmed or split. Part of the hobby?
For the PH, I would advise strongly against trying to change it. It would be a special burden for one who might be gone now and then. Leaving adjustments of that sort to others is especially scary as well as being constant work for you. I find no problems with 7.8 water with lots of liquid limestone!
On the cycle question, there are many ways to go depending on future plans. Just letting the plants and tank get going will allow you to more or less safely add a few fish. But if you need to order fish or plan to buy more than a few at a time, the tank will not be ready for a sudden increase in bio-load. A fishless cycle may seem tedious but it is the one way to deal with getting ready for a big increase. The good bacteria only grow to the amount they are needed in the tank at the time. It will "cycle" but not to an amount that will support what many of us would call a full load. Depends on your future plan which way you need to go.
But it is always super good to avoid trouble when you can. Keeping fish healthy is far, far , easier than helping them recover.