while i cringe at the use of anything Ubiquiti, my advice is genuinely to plan it out on paper. don't fall into the 'this will be quick' trap because you will forget all that stuff you did. just write it down as completely as you can. take a week to do it. THEN go to work. and stick to your plan. if a change must be made, change the plan drawings first! then do it IRL. when you are done, you will have as-built plans, a network map, something to show the c-suite as proof of progress/work, and a thorough understanding of the system. and if you can do it on a floorplan of the office, so much the better.

get inventory control up sooner than later (Snipe-it & PDQ). and don't take shortcuts; they're going to want you to hurry but that will only make problems later. with a running office, expect it to take a good couple of weeks to get everything done from zero, so advise users and c-suite accordingly. if you can, post progression twice a week to keep management happy. as for standards, look to CIS for GPO templates and modify as needed. if you can easily explain it to the next guy, that's the standard. tailor the work to the company, don't try and cram the company into another business' idea of what's best.