Welcome to the forum. Here is the way I do it, of course everybody has a comfort zone given by their trust in equipment, trust in themselves, cash and time.
For most parameters, testing with aquarium grade test kits is like walking in the dark trying to find the sink and the towel (had another image in my head, but let's keep things family friendly). What the test kit shows is around the value that is actually in the aquarium. How much are they off is a function of many other parameters. However, most test kits nowadays have a systematic error for the same aquarium water. That is to say, if today you measure your aquarium with test kit A and it has 10pmm, and tomorrow on the same aquarium with the same test kit you have 30ppm then you can say it increased. It would be wrong to say in increased with exactly 20ppm. Thus good to make an idea, bad to make a decision. There are other ways of measuring the conc. in water but prepare to put some heavy cash aside. Another good option if you really feel you need an accurate image of what is in a tank is to have your water tested at a local water lab or uni.
Instead of relying on the known inaccurate testkit I find that it is better to know what you put in the aquarium and put enough of it to feed the plants. A mature tank should have ammonia at 0 all the time. A ph crash can be avoided by having good KH ~3 or more. Also know that most of the pH values for freshwater fish on sites are based on either dreamt up values or what happened to work for that person. If the site says 6.4-7.2, nothing bad will happen if the pH is 7.5 promise.
I would go with the electronic meters, as long as you understand what they measure and how. The pH pen needs to be calibrated and replaced, the confidence interval for most of the cheap pens would be +/- 0.5 . The TDS meter actually measures conductivity and should provide an estimate of all substances that are in the water column and conduct electricity. It is a great fast read of your aquarium. In a way, it is like me saying all the edges of my room have a length of 180m . Big room , yes. Can you say if a piece of furniture with a height of 3m fits in ? No, because like TDS it does not give a detailed picture of individual measurements/nutrients.
That being said, I find I frequently use a TDS meter, a pH pen /probe, a KH and GH tests (because I use RO water). Ammonia tests can be used if you are in a hurry to start up a new tank but not absolutely necessary.