Some drawings might help. In today's market you can get SIP's that are only 4.5" thick and still present R25 or better when you add the internal drywall and any reasonable exterior finish (siding, stucco or whatever). The SIP's usually are installed on a 2x toe which is firmly fastened to the sill plate. Don't forget the closed cell foam air dam under the toe. About 1/2 of the outer thickness of the SIP plus the exterior finish is outside of the outer edge of the sill plate. You may want to consider offsetting the inside face of the SIP's from the outside face of the posts by 5/8" for later insertion of drywall (added insulation and ease of finishing).
This same SIP vendor will include plastic conduit for wire chases and/or a sprinkler system built to your plans and formed inside of the SIPs from the get go.Window and doors are now "standard" thickness jambs. Saves hours and lotsa routing/foam filling you don't have to do. Send me an email for the company name. They advertise in TFG publications. The outer face of the ICFs can be protected with 1" high density panels and an elastomeric coating forever waterPROOF below grade, especially if you add the proper compound to your concrete mix (cost about $30 per 5-7 yard load). This additive changes the crystalline structure of the concrete as it cures so it is also forever waterproof and will not effloresce over time. Anchoring the post bottoms offers several alternatives. If you are in an active seismic area you may want to consider reinforced concrete columns in the foundation walls all the way to the footers. If the floor joist system sits on top of the foundation then a "box" around the post bottom is an easy setup. Further horizontal and vertical movement of the posts is inhibited by lags thru the band and floor joists.
This is one of several methods that work.
Work safe, have fun.
