At what temperature do you need to cover and protect an in ground fig or bring them into your garage (if in containers)? I have friends I hope to gift some figs to (and spread the disease of fig lovers) but they live in different climates than me. I don't worry about temps getting too cold here but my friends might.

How cold is cold for you? for you wife? Probably different. Same thing for different varieties of figs. There are reports of trees taking down to zero F. Most people back east seem to want to keep the above 32F, but suggest that they survive with minimal damage at some point below that. Depends on your tolerance for risk.  There are no studies that I am aware of.

That is a good point, I forgot that some varieties are more cold hardy than others.
One person I am asking for, goes into the 20s for winter night time lows, central Oregon. My hunch is the average fig would need to be covered or brought in, unless the variety is specifically cold hardy.

For my rare trees, if they are in 2gallon or smaller containers, I bring them inside at temps lower than 28 degrees. Not so rare trees are left outside at any temps. This is what I do for my area and it works for me. Hope this helps.

Does size matter?

I have figs in all stages, cups/roots and leaves, 1 gallon, 2 gallon, 5 gallon, my concern is that all of my trees have new growth on them as I moved them all into a 78 deg well lighted (24/7) environment.  I am concerned about the new growth even at 35 deg.  It is not so much the leaves as the potential  harm to the root system in the cups and smaller pots.  I use the cups as gateway plants (give a ways) to entice newbies into the hobby so I try to keep 25-30 at all times.

I think that just a basic minimum temperature helps, but you have to also consider the time they stay at that temperature. My potted figs have withstood 22 F so far this year, but were that low for only for an hour with a warm up to 45 the next day.

I usually get nervous and bring potted figs into the garage when temperatures are in the lower 20's  (below 24 F) for any significant time period. I have not experienced (not yet) any loss from cold temperatures, although the pots appear solidly frozen at times, it is not for any extended period. In ground figs have to tough it out. Record lows here are single digit and below, but generally, in a cold winter, temperatures might drop into the teens for a few hours. The damage I have seen in in ground figs are almost exclusively in figs on the south side of the house as they warm up during the day, temperatures drop rapidly overnight and there may be freeze damage.

As an example, this little Hardy Chicago has not even lost its last leaf so far this winter. It has withstood 22 degrees F (but just for an hour).

That is one tough little baby figlet!