Uploading supporting docs- applying from USA

Hi, this is my first post and I apologise if this is covered elsewhere. I've done a search and couldn't find the information I was looking for.

My US fiance,Bill,has submitted his application and booked his appointment for April 9th. We are currently gathering all the supporting documents required and I believe we have most things covered. When looking at different sites for advice I've come across some confusing/conflicting information so hope someone experienced can help clarify.

1) Do we need to submit copies of our evidence pack ?
Some sites say to make two packs, one with originals and the second a copy of the first. From what I can read Bill will be sending the supporting docs to New York for scanning so not sure the purpose of providing 2 copies ad wondered if this was outdate advice.
2) Evidence of marriage plans
This is a second marriage for both of us. We are in our 50's so plan just to go to the registrar with 2 witnesses, one of whom is my son. I have emails between the Bill and I and the local registrar discussing requirements and have been told we can book the registrar with copies of the marriage notice and required docs as long as the originals and visa are presented before the wedding date. They can move the date if there are any delays with the visa. We will have a more public blessing at a later date but haven't made a decision on what that will look like yet. I plan to submit the email conversation along with the booking invoice as evidence of intent to marry. Will this be enough evidence or do I need to provide witness statements to back it up ?
3) Relationship evidence
Bill and I have known each other since we were teenagers (38yrs) both us have come out of bad relationships in the last year (he divorced and I'm widowed.) We have been good friends for the last 10yrs but it only recently (last 5 months)that this has developed to the point that we want to spend the rest of our lives together. I have to admit to being a bit concerned as to how this will be viewed by the entry clearance officer. I can provide evidence of how long we have known each other, our 10yr fb based friendship and our more recent romantic relationship through Messenger logs, photos and plane ticket receipts. We will both write cover letters outlining how our relationship developed. Any further advice on this would be appreciated.
Thank you in advance
Nicky

How about the financial & accommodation requirement? Are you working & having sufficient accomodation??

Yes, I more than meet the financial requirements and have the relevant payslips,signed letter from employer confirming salary, length of service and how long I've been paid that salary, job title and that the online payslips are authentic, and bank statements required. I've tenancy agreement,letter from landlord for accommodation and latest council tax bill.
I'm confident that this is meets the requirements if the immigration laws in this respect
Again if I've missed anything I'd appreciate advice
Thanks

My fiance has received his biometric appointment confirmation which contains a link for him to upload his supporting docs. Does anyone have experience with the process and able to clarify a few things for me please.

Should the docs be uploaded before or after his biometric appointment ?

Do the docs all have to be uploaded together at the same time or will the system accept more than one upload. E.g. can he upload his information then upload the docs I have to send him seperately?

Any other advice would be appreciated

Thanks
Nicky