Some additional notes for that method though:
The strap itself should not be going over the condom. Even though it might feel secure, as lube will leak onto it, the condom will eventualy cause the sleeve to slide if the condom was gripped by the strap itself. The strap needs to have direct contact with the sleeve.
The strap type doesnt realy matter here, both work fine (the new strap is the one i prefer, but thats for other reasons)
Ensure that the condom gives enough space for your dick, there should be no resistance (touching is fine though, you dont want to have a too long end piece as that might be flapping around). If no room is given, you might push the condom out of its position (if that happens you can unroll it a bit further though and strap it over again, but by that time some lube will have leaked…
Even if its only a small portion of the sleeve it is strapped over, as long as there is a strong gripping point (a clear edge) the rim of the condom due to being less stretchable will provide enough force to not be pushed away. Especialy when your dick isnt pushing, it barely even needs any force to stay in place.
A condom has no perfect seal, it has a chance of fluids leaking out of it. After all the sleeve is soft and the gripping point might not always be perfect. This mostly depends on condom size though, the tighter it is, the less chance. But too tight will interact with the sleeve itself. This is something you only will know through testing. For this a size testing box for condoms could help (ie. a box with sizes 53,57,60 - as 53 is the average, and you generaly want a size bigger to give the sleeve some room).
And if anything is leaking, instead of splashing it around, the sleeve usualy soaks it up. It might then get sticky and require some washing. But thats something i would recommend doing occasionaly with closed sleeves anyway.
From my experience, i only had a leak once, and that was because after the cumshot i did let it go on for a while. This was at least for 10mins and only made the strap feel a little bit wet. I just rinsed it once with tap water and it never got sticky. If you are realy worried, just have 2 straps so if 1 does get dirty you can clean it and have it dry properly and just use the other strap in the meantime.
Also, any short open ended sleeve feels a lot like a hand because of the short length. A hand usualy gives a very clear stroke position. But other than that, no sleeve will truly feel like a hand, the material just doesnt feel the same as a skin. But it doesnt matter that much anyway, as long as the sleeve itself feels good, it surely does the job. But the feeling of an open ended sleeve differs that much from a closed end one, its realy worth trying.