I have a 24" cabinet for the microdrawer and all drawer bases of different sizes. (The corner next to the hob is a door made to look like drawers - we have three pulls on it - so that the flow of the bases goes all the way around the kitchen. It houses a magic corner unit.) Here's a picture of what it looks like: You need to decide what look you want. You'll have more storage (in the drawer next to the microwave) if you have 24" and 30" though and for us storage was a priority.

You should be able to install a 30" microwave in a 30" cabinet (my 24" drawer microwave is installed in a 24" cabinet). Note that the "guts" of the 30" drawer microwave is identical to the guts of the 24" version -- only the trim is different.

It depends on the type of cabinet. Full overlay = same size as apron sink Different cabinets have a notch out for sink & use a wider cabinet, example

Annette, if you have decided to use Ikea, you need to build your design within the Ikea planner so that you are working with their cabinet dimensions. Unfortunately, you are a half inch short on the W/D wall to use the tall cover panel to enclose it for that run. The fridge cab, cover panel, and corner cab is 30+.5+38=68.5. Your wall is 68". An alternative is to eliminate the cover panel or just run it down to the counter. You might be able to gain 1/2" if you do not install the bases on the window wall using the rail system. The rail protrudes 1/2". With pulling the corner cab out from the wall 6", you will either have to mount a 2x4 frame to the wall to mount the rail and cabs to or secure the cabs to the floor using this kit or something else you devise. The bases that you will install as uppers will not need the extra framing since you will be able to mount the rail to the wall. I have no knowledge of log cabinet wall construction but I'm assuming studs aren't involved? Will your contractor guy be doing the install? Here is the link to the above plan. The planner does not have the capability of moving the base cabs up the wall, so I configured it with wall cabs as placeholders and pulled them out 6" to allow for the 24" depth. Subtract them out from the item list and add three 12" base pullouts . I added a free-standing 12" base pullout in the plan with counter and legs removed so you can see the item numbers. Add three of those to the list. They come to $163 ea using Grimslov doors. This plan comes to around $1500 without counter and handles. Whenever I do changes to their standard configurations I create the plan, print the item list, then add my changes to the printed list. Bring that with to the store and the associate will be able look it over for anything missed and do your additions/deletions. Here is the link to the plan using two 15" pullouts instead. They are configured with the bottom drawer attached to the door and two additional inner drawers. If you don't have their current cabinet catalog, here is a link. I don't find a new one with their newest door style. I hope this makes sense! Let me know if you have questions.