Is it harmful to follow several programs

Harmful? Probably not, but the programs are designed around certain gains or changes over a period of time, so they might not be as effective. There is of course the risk of overtraining but that is true in general.

I dont know your present level of fitness but those three programs together should be ok.

Thank you for the quick response. I also feel those 3 should be Ok.

In addition to he programs, there are different training plans you can use, according to your goals (general fitness, strength/tone ...).
So let's say you want to improve your general fitness, so you choose 'The Guardian' template. That calls for a 'Strength Workout' on day1. You then go to the workout page and use the filter feature:



Then you filter the workouts by type (= Strength/Tone), difficulty (let's say Level 2) and by focus. Let's say, you want to make Monday your 'Leg-day', you choose 'Lower Body' and tataaa:
17 workouts to choose from. Even less if you consider a classic or circuit workout.
The rest is up to your gusto.
Use the same method to fill the other days and you got your first hand-tailored, bespoke workout week.

Keep in mind, that the bee-keepers put a lot of thought into those programs, so your self-made plan might not as efficient as they are.
I'd suggest you keep a training-log like an Excel-sheet, Google sheets or sheets of paper, if you are old-school. It helps to keep things tidy and is fun to read, when you are a tough level 5 athlete.
All the best
Andi

Thank you Andi64. Now i think I get the idea how to use the workouts.