Never really been a cat lover to be honest. I see my neighbours cat daily when it comes to shit in my garden, which I then have to tell my neighbour to come and clean it up on a daily occurance.
Regards a microchip flap, I would say is a good idea from an owners point of view as it will hopefully keep other cats and unwants pests out. FWIW mate the closer pets one had a better review score of 4.4/5 than the others when i did a quick search on Amazon.
My dog got killed because of a cat when I was a young lad of 7, it may sound silly now but I still have that thought in my head and probably the reason why I’m not a lover at all of cats sorry.