Bob seems to have covered most of the points that need to be covered for now. It is unlikely that your medics would recommend irrigation for at least 6-8weeks post operation, so you still need to take notice of the advice people are giving with regard to your immediate problem. In any case, unless you are very fortunate with regard to irrigation, it is as well to have all the problems with the bags covered before you reach that point, as you might need to revert back to bags periodically.
Having said that, I would highly recommend irrigation at the earliest opportunity, and there are a number of useful youtube videos explaining what that is all about.
As for 'bag' leaks, I tried all sorts of different things, but eventually made my own baseplates to suit 'my' needs.
They are not difficult to make, but need a lot of 'tweaking' to get them to work for my specific requirements. So, I would suggest you try all the manufacturer's 'freebies' before embarking on a DIY route, as very often there will be something already out there, which will save you a lot of time, thought, energy, and frustration overcoming mistakes before you come up with something that suits you.
I sorted my bedtime leaking problem partly by purchasing a new bed, which elevates both feet and head. This keeps me effectively lying on my back in one position all night. ( a bit like a hammock ) Not a position for everyone but it suits me for three main reasons:
1) It allows the flow of output from the stoma to enter the 'bag' without obstruction. (The night-bag in my case is a folded irrigation sleeve - which is huge as a bag).
2) I have sleep apnoea and this position helps keeps the nasal pads in the right position all night - so I GET A GOOD NIGHT'S SLEEP.
3) I suffer with a hiatus hernia and this position prevents severe reflux without having to take medication for that purpose.
I hope this is helpful, but I also hope that others have more suggestions as to what you can try regarding the leakages.