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That would depend on what type of plants you have. Some plants like the cold weather, while others need to be protected from the cold winter weather. If you have a wisteria, then by all means, plant it outside; the same goes for pampas grass, touch me not, and poppy.

Advantages of container grown trees over B&B:
more maneuverable
easier to have been kept watered
rootball less likely to break open
Disadvantage of container grown over B&B
can become too rootbound, will have to loosen roots
Staking
depending on trunk diameter, 2 or 3 stakes. use aluminum wire with
section of old water hose over wire where touching trunk
do not stretch wire taut, leave a little loose
leave stakes 2-3 years depending on tree size
not as attractive in landscape, but important to tree

When potting containers for windy locations we use a large rock or brick in the bottom to add weight. If it isn't convenient to repot, add a 2" layer of gravel to the top of the soil. Water the plant if the soil is dry, even if it is winter.

It depends on what plants you plan on using. If annuals will be used, I suggest using equal parts potting soil and top soil. Using a quality (commercial), peat-lite potting soil with sterilized top soil makes a mix that is easy to use, yet heavy enough to hold moisture. You can definitely use compost instead of the potting soil. Sterile top soil will reduce weeds and pathogens.
If the planters are concrete, I line them with a thick trash liner. This keeps the soil from being to alkaline from the lime in concrete. Just be sure to poke drain holes in the liner.
If you use plants with a 'drinking problem', like petunias, consider using one of the moisture retaining polymers. Also, if you use plants that need lots of nutrition, add a time release fertilizer to supplement water soluble plant food.

Without glazing the entire pot, moisture will get into the porous clay.

Use organic-rich potting soil for container plants. This article should help with the fungal gnats: https://www.gardeningknowhow.com/special/children/fungus-gnats.htm In addition, neem oil should help take care of these bothersome insects: https://www.gardeningknowhow.com/problems/pests/neem-oil-uses.htm