On a BT 5270, I used a ladder mounted rack at first, and this is only my personal opinion, many others must successfully use them, but I had two major problems.
I don't remember the brand, it was purchased at a Camping World store, it was specifically for bicycles.
First, with the ladder mounted rack , you need to lift the bike very high, it rides vertically. I had extreme difficulty mounting two adult bikes.
Second, I did not feel the whole assembly was secure, it seemed a bit light weight for the job it had to do, only two little straps held the bike on, and it put extra strain on the ladder. I had everything connected as instructed, plus added bungies.
So I went to a hitch mounted rack. Swagman, where a top flat bar screws down tight over the bike frame - and locks - a plus. The lock is built into the top screw ( don't know if they still make them that way).
It works so much better for me.
Eventually I added a hitch stabilizer which got rid of the wobble, which had not caused a problem, I just didn't like the tiny slack in the receiver that allowed it to wobble a bit. That is listed on Amazon as :
"Towever 84701 Corrosion Resistant Trailer Hitch Tightener Stabilizer Cross Clamp Anti Rattle, Zinc Nickel Hardware for 1.25 inches & 2 inches Hitch " It is a heavy duty device, and I recommend it.
Then I started towing a car, so I got the hitch extension that has two receivers, the lower straight through one for the tow bar, and the upper one for the bike rack. I paid what I felt was a lot for the extension, but after looking at cheaper ones on the internet, I read they had problems with those breaking - so I'm glad I got the expensive but well built one at an RV dealer.
I hope this helps.