You never knows. Normally I start this way and later increase or reduce bids based on my average position and conversion rate. 50-100 clicks will show you the perfomance. And it's better start with 10-15 main keywords to see how it goes and then expand from here to longtails
I generally do the same when introducing new Adgroups or keywords for clients, I'll start low and increase the bids after gathering average position stats for the day.
Yes, you can use the traffic estimation. Anyway traffic estimation tool can only give you roughly information. You have to set the bid and check the impression from your log file to make sure you can control the impression that you want. Another way is to set up a proper daily budget, but again you have to check the stat if you really want to make the campaigns work with the impression.