The seat of the BuggyBoard Maxi is removable. It is attached with a special clamping system that allows the seat to be quickly fitted or removed to switch between sitting and standing. The slide or click buttons you mentioned may not be visible in all pictures, but the system is designed to flexibly attach and detach the seat.
Never even noticed it. I do not believe it is relevant. However, I can share my experienced with this product. This product will make the stirring of the stroller a bit difficult. We have an Uppa Baby stroller and the fit is not the best, installation required some hustle and cursing. My advise would be to buy it in a store, if possible , and try it on your stroller before buying it.
Normally, it should be able to adapt.
However, if you require extra space for the saddle (seat), you can add an extra extension kit to extend the board arm which can give more space.
So the items should be compatible, and if you need the extra space, you can get these extensions: Lascal BuggyBoard Extension Kit
The manufacturer states that this product is compatible with most prams on the market.
However, it does not specify whether it is compatible with the two models you mentioned. Therefore, we cannot guarantee this.
According to the manufacturer, this product is compatible with almost all prams.
However, it does not indicate whether this product is compatible with the Jogger City pram.