Lastly with the lie flat seat vs carrycot, again depends on a few things.
First of all some of the pushchairs on the market don't have a proper lie flat recline, they just have this sort of moulded seat which tilts back. I wouldn't let this kind of seat replace a carrycot. You can sometimes get an insert which flattens it out more for newborns.
Some pushchairs have a clever thing where they have one frame and either two sets of fabric that strap to it or one piece that opens out into a carrycot vs a more moulded seat. These are good if it's space/cost saving you want but you do want the benefits of a carrycot.
Then some have the kind of seat where there's a hinged bit in the seat itself so the backrest can be moved up and down. These can be used in place of a carrycot.
A proper carrycot will generally have a mattress and no straps so the baby is free to move/roll around. This is good for development, but not great if you need to bump the pram up/down steps or steep slopes because they slide around in it.
Some of them are also certified for overnight sleep which can be useful for peace of mind if they nap in it (if it's not certified, then you should supervise them if they nap in it).
They often have more "contained" sides so the baby is a bit more protected from wind, noise etc. Whereas the hinged type or the moulded seat with newborn flattening insert often just has the hood for protection and might be less cosy. If you have the chance to try the pram out in all different modes before buying it's worth doing. Even if you decide to buy online or second hand, it's worth having a play with some different models in a local shop to see what they are like.
Some carrycots are big and roomy, so you can keep using them up to about 9 months first with baby in a sitting position and second with them lying on their front. (I've only seen people doing this in Germany though, never in the UK - big prams like Gesslein or Emmaljunga). Most of them are small and only accommodate babies up to about 3 months old. If you have a very long baby or one that likes to fling their arms out and gets angry at being contained, it might not last long at all.
You can wash the sheet of a carrycot mattress easily (a pillowcase also fits) whereas sometimes the fabrics on pushchair seats are sponge clean only, so they can be more practical for reflux babies. However OTOH reflux babies commonly hate lying flat.
With the hinged type, you usually have the option to tilt it up a little bit to a similar angle like a car seat. I quite liked doing this with DS1 when he got to about 3-4 months old. When he fell asleep, I'd lie it flat again. The downside of the "one frame two seats" type is that you often don't have this in between option, they are either flat in the carrycot, or very upright in the main seat.
If you're having them in the main seat part laid flat with straps on, then you should make sure they do have some chance to lie flat and unrestricted every day. Of course their night time sleep space should be like that, but they need some daytime play in that position too to help them learn to roll, sit, lift their heads up etc. So if you're likely to spend a lot of time with them in the pram, a carrycot might be more necessary vs if you see yourself spending more time at home.