47re transmissions are 100% compatible with 48re converters.
48re transmission are compatible with 47re converters however, there is a seal on the stator support of a 48re transmission that is designed to help seal the stator shaft to the inside of the torque converter; 47re converters are larger diameter in the region where this seal rides so the 48 seal no longer seals. This is not a major issue other than lowering the converter pressure a little similar to what a 47rh or 47re transmission normally sees. Many racing and hot street performance 48re transmissions are built and sent out the door with the stator seal missing on purpose. For good measure, when installing a 47re converter on a 48re transmission, most guys spend the 10 seconds to remove the stator seal so it doesn't have the possibility of popping free and potentially ending up somewhere else in the transmission.
To fix your 2-3 bind issue, you can make small improvement by loosening the band adjustment try 2.5 loosened from 72 inch pounds. For major improvement, you'll need to increase the 2nd servo release spring tension (double spring), change to a different style servo and/or lever ratio, or slow down the 3rd gear apply circuit (
VB modification or restrictor orifice on 3rd apply passage).
To answer your second question, depending on the stall speed of your converter, it will never pull as hard unlocked as in lockup. If you have a higher than stock stall speed, like a 2400 V-10, you could be down as much as 200 HP unlocked vs locked on a 1000 HP truck. With a 1600 to 1800 stall converter, you'll still be down 50 to 75 HP unlocked vs locked on a 600 HP truck. By design, a torque converter is designed to slip when not in lockup, that's how it multiplies torque. If you get a super low stall/highly efficient torque converter, it will have much less loss unlocked vs locked, but it will also bog and cause the truck to act sluggish/increase turbo lag at low rpm conditions.