ADFS internal and external users

Thanks footech, appreciate the help and that all makes sense ans is as I expected from reading design blogs/technet articles.

Regarding:
For an external user, adfs.company.com would resolve to the public IP of the WAP (ADFS Proxy), but for internal users it would resolve to the internal ADFS.  If you just had internal users, the WAP wouldn't be needed, and no, communication to the internal ADFS from the internet is not needed.

My question is:
With the internal users in this scenario, what happens to the traffic once they've hit the internal ADFS farm. Does it still then go out via the WAF?
I assume it's only the WAF that can access the RP in this case and we don't need to also allow comms between the internal ADFS farm and the RP as well as comms between the WAF and the RP?

Again, thanks for the support.
Andy

Thanks footech,

Just one final question:

We have our main domain, and 2 sub domains, do we have to setup anything extra for users, either in ADFS or DNS?
e.g.
uk.comany.com (root domain containing accounts)
us.company.com (sub domain containing accounts)
china.company.com (sub domain containing accounts)

My design steps (as an overview) are as follows:
Create the service account (or gMSA)
Build the 4 2012 R2 servers required for ADFS 3.0 (2 x Internal, 2 x DMZ)
Decide on the public ADFS (federation) service name:
Adfs.company.com/sts.company.com/sso.company.com
Buy certificate
Import the cert on each server
Consideration: Multiple domains
Setup DNS entries as required (internal, DMZ, external)
Allow port 443 between all devices and externally from WAP farm VIP
Consideration: NLB used in DMZ? If so, setup NLB on both servers with VIP
Add the ADFS role for the first internal ADFS server creating a farm
Configure ADFS with SSL Cert, Federation service name, Federation service display name
Specify Service account, WID. Complete configuration
Test: https://adfs.company.com/federationmetadata/2007-06/federationmetadata.xml
Add the ADFS role for the second internal ADFS server joining the farm and configure
Add to Load Balancer creating the Load balanced VIP
Add the WAP role for the first internal ADFS server creating a farm
Add the WAP role for the second internal ADFS server joining the farm
Test SSO internally
Test SSO externally?
Send metadata to SaaS provider, configure and test.

Hopefully I've got everything there.

Thanks again,
Andy

Thanks for all the expert comments, my design is getting there, just need to understand what data is being passed between all points then all will be complete.