Double buggy 20 month gap advice please

hi

im after some advice from people who have been there! We are due our 2nd child in January and there will be a 20 month gap between the new baby and our little boy. 16 months At the moment he is walking but still relies a lot on the pushchair.

will I need a double buggy? It’s going to be winter so we won’t be out for long When we are.

do I get a buggyboard?

do I rely on a sling for new baby?

i was looking at cheaper double strollers but I relied on keeping my son asleep in his car seat a lot so I’m thinking about getting another travel system now but it’s the cost!

any advice would be great thank you!