I've also tried all market centers. Is this a viable strategy?
As noted previously in several other threads and by reference above, this strategy is more viable the more planets you have in a star system. If the random generator kicks out rare stars, rare planets, and rare habitable - you've got very little chance of getting this strategy to work. However, Mumble made me curious, and you CAN get this to work with as little as 200 planets on a medium sized map. The key is to be smart with your money, and focus on tech.
But, of course, if you've tried it, you should know if it is a viable strategy. Was it for you?
Is the all market strategies inferior to other strategies?
What do you mean by inferior? All of the strategies have their strengths and weaknesses in different situations. Plus, just knowing how you plan to build your planetary tiles at some point isn't enough. I usually rebuild all of my worlds at least once, so listing a set "build" is deceptive because it is only a snapshot of an overall strategy, for instance.
With all labs, what should I do with my space miner?
you can still have it mine, upgrade it to a different ship, leave it in orbit to defend a planet, or even sell it for a few dozen credits. It probably will make very little difference no matter what you do - it's just one ship.
In all labs and all factories, how many star ports should I build?
Another question with no right or wrong answer. I mean no offense, but I think you don't understand the depth that exists within an "all labs" strategy, or any of the others. There is much more to the game then deciding how to allocate your sliders. For instance, there are at least 4 different ways I play an all labs strategy - depending on the situation:
1) Build several labs (at least 3) on every planet, with stock markets on most planets, so that every planet can produce something (social or military) at all points.
2) Build a few dozen core worlds filled with labs (every tile save one starport), and have every other world in your empire be all stock markets to pay for the production.
3) Pump up your military and social production bonuses, and then fill the universe with 2-4 econ starbases per quadrant... but only build one or two labs per world.
4) Create just one system that will produce everything - with a large (PQ26+) planet that gets all the tech super buildings, and surround that system with at least 16 economy starbases. Nothing else needs to be anything but stock markets - but place your wonders on garbage stock market worlds, where they don't take a precious lab tile.
Each one of these approaches has different strengths and weaknesses depending on the number of planets you have available, the spread of bonuses you are using, the average number of tiles available on each world, the amount of surplus money you have, the number of enemies you are fighting, what you super abilities are, etc. etc. "All labs" or "all factories" isn't just one strategy. I'm sure there are more approaches I don't use, a lot depends on personal style and game situation.
You might as well ask: When building a mix of factories and labs, how many starports should I build? It depends.
Do I have to take control of my survey ships and scout ships?
Why are you using scout ships? IMO, that is a waste of an early game resource. As for survey ships, there are advantages to micromanaging it. Its up to you whether the "annoyance" of micromanaging is worth the beneifits, or whether Auto Survey is good enough for you. I could tell you my personal taste, but ultimately its a question you have to answer for yourself.
There are already some very good responses to your question by veteran players above. If you are new to trying these strategies, I strongly recommend starting with an all factory approach - it has fewer weaknesses and is easier to pull off. All labs is more powerful, but a lot tricker to use, and I definetly think is a more advanced approach. Prepare to fail the first couple of times while you work out the kinks. Very broadly speaking all factories and all econ are easier the more worlds there are, where as all labs is often easier with less planets. It depends on how much money you can make, what galactic resources are available, how many planets there are, how fast you need to produce anything, etc.
I'm not really trying to get all Zen on you here, but seriously, experience is the best teacher. Skipping straight to suicidal is, well, suicidal. You say you already play with these strategies... so figure out what works and what doesn't in the game environments you are generating. Unless you give a very detailed situation, the best people can do is wax poetic about their own favorite approaches in the game environments they create for themselves.
Good luck out there. If you have a more detailed situation you need help with, I'm sure there will be people who will answer any questions.