I can’t answer your questions about the architect/meetings/etc. Some provide you with plans and that is the extent of their involvement. Some will make regular inspections at critical times (prior to pouring the slab, during the framing, before drywall, etc). Some will set a limit on the number of onsite visits they have to make. Others will act as the builder and do the job of the General Contractor, hiring subcontractors, purchasing materials, scheduling etc. It depends on the individual architect and what his contract with you says.
As for whether the plans will be perfect the answer is no. Most architects I have had dealings with just cut and paste from one job to the next so usually there is something left out or conversely something included that does not need to be there. I have also found that there are architects out there who, while they may know how to draw, they have no practical knowledge regarding actual construction and what it takes to construct a three dimensional object from their two dimensional plans. Simple things like you can’t put a three foot door in a three foot wall (you need room for the door, the framing members and the door frame, not to mention the trim). And sometimes you just can’t put a switch exactly where it is show because of some conflict. Most are practical and as long as it looks like what is on paper they are fine with it but every once in a while you get a prima-donna who will say something like “Well that’s the way it is drawn, you should have brought it up when you were bidding it” or my personal favorite “I don’t care how you do it just do it the way I drew it’! (Ya know, if I could do that I would not have brought it up to you in the first place).
Take the plans home and study them and if you see something glaring or missing or if you want to have a 3-way switch or think a row of recessed cans would look good in the dining room have the architect put it on the plans before it goes out to bid. Same goes for every other sheet. Add doors/windows/wood flooring/tile surrounds/relocate walls, etc while it is still on paper not while construction is in process. Also, expect to miss something and have to change it. Set aside some $$$ for items missed or things that you suddenly realize you can’t live without.
Most home plans, particularly those custom ordered, will have an electrical plan. It will show switch, outlet and fixture locations. It will indicate whether you have a light, ceiling fan or ceiling fan with light and if the latter whether it is controlled by two switches or one.
Outlet spacing is set by code and most of the time the electricians will try to get them as close to where they are shown but unless they know going into it that they have to they will not place them exactly where they are show; they will go alongside the nearest stud. Switch height and outlet heights are usually set by code but there is some flexibility in the vertical location just be sure you have them set where you want if you want something other than the standard location.
As for the actual fixtures, there are two main ways of doing this. Either the architect will specify exactly what brand, style, model etc. he wants or he will specify a fixture allowance so that the contractor will know how much to include in his price and you will have some flexibility in choosing exactly what you want.
Most homebuilder subcontractors are used to homeowners coming in and making changes and, if it is done beforehand, and no additional cost involved, they are willing to make the change. What I am trying to say is that if you want to locate a switch from one side of an opening to the other side there should not be any cost involved unless the switch is already wired in (if they only have the box nailed to the stud, no charge, unless they are a-holes or the architect has been an a-hole to them). However, if you want to add another switch to the other side of the room they will probably pop you a few bucks. Most contractors who have been building homes for a while will have a little money set aside to make unforeseen changes that the know the “little lady” will have to make but also be aware that none will admit to it.
Remember that it is your home that is being built and that you are paying for it. You can walk through it whenever you want, as many times as you want and if you see something that you do not think is right let your builder know immediately,
Also, if you bring cokes for the guys actually doing the work it is a cheap goodwill gesture and you can get little changes made just by asking them without actually involving the “bosses” if you have a good relationship with the workers.