Q1. Is there a way to build business applications against SharePoint, where the users may be disconnected/ offline ?
Answer: Yes. You can use the client side pattern I discussed with BCS, and it does support offline scenarios. Please see link below for details.
Q2. Do we have guidance to capacity plan for Access Services ?
We do have some guidance from SharePoint 2010 days, which can be used as a start for 2013. However I haven’t seen any guidance so far for SharePoint 2013
Q3. What kind of app does Access Service create? Auto/Provider hosted or SharePoint hosted ?
Answer. Access services create a SharePoint hosted app. If you are on premises you will need to configure your environment to host your apps. This blog from my good friend Kirk Evans, discusses how to host your Access Services on premises. Note the section where he talks about configuring for apps.