A 20 gallon will work fine. You can go with something bigger if you like, but it'll mostly be just for display. They tend to stick to the safety of their burrow.
Tarantulas are also nocturnal. So they really only wander out at night.
If your T is wandering the tank endlessly during the daytime, then something is wrong. Usually has to do with an inadequate hide.
You can feed it a pinkie once a month. Not too many too quickly though. Vertebrates are high in calcium, which can actually harm a tarantula. Too much calcium can cause things like fang deformities and dangerous molting issues.
L. parahybana does have a juicy appetite though. So feed it about 6 crickets every Friday, with a pinkie substitute every 3-4 weeks.
I did find a pic of my female L. parahybana when she was just a juvenile.
Her eggsac held over 500 slings.
Yes they have 8 legs, but so do fleas, ticks, and scorpions.
Tarantulas are theraphosids, spiders are theraphosidae.
So one is a "tarantula", the others are called "true spiders".
I don't do true spiders either. I like the large ones so I know where they are at all times!
p.S.. There's no such thing as a deadly tarantula.
As far as I know, there are no recorded human deaths from a tarantula bite.
Only spider bite fatalities have been documented.
But I've been out of the loop for awhile, so that may have changed.