Ive been on TRT for a year now (160mg/wk, 1000iu hcg/wk) and I run tren cycles (500-700mg) a few times throughout the year. Never had any issues. I get bloods done every 12 weeks and everything always comes back great.

Are you planning on doing a cycle of test then? You can mix the esters, you might want to drop down the prop a bit. I run tren cycles, drop the prop a little, and continue my TRT protocol without any issues. It's all up to you, I experiment with short 6 week cycles first to see how it goes, and then go for a longer run if I like what I'm seeing.
Then when I go bloods for the doc, I make sure I give it a few weeks to clear out, and be on my TRT cruise.

That would really depend on your goal. The more test you add the more you will blow up, but the bigger chances of sides such as estro and prolactin issues.
I wouldn't really consider testosterone gel a cycle, so it will actually be your first cycle and I wouldn't recommend 19-nor for the first cycle. Why don't you put the npp away for another time and just run basic 500 mg a week test cycle? It is good option for beginners. You will learn how your body reacts to higher test dose as well how sensitive is your body to sides including estro. You didn't mention any auxilaries. Do You have any ai?
Don't rush into it. 19-nors such as deca, npp, tren can hit you back with nasty sides such as limp dick, loss of libido and even lactation. You have to worry about more things than with simple test cycle, which alone should give you excellent results as a first cycle, given that you diet and training are spot on.

How long have you been on the cyp
If its DR prescribed why be in a rush to add more. See how you make out first

I'm assuming this is going to be your first cycle. Would help to know your current stats, including Bodyfat, and your diet and training protocol to see if you are even ready to run a cycle yet.