Ironlord, I think “biscuits” are a thing of the new. Their installation requires a “rotary cutter” and that is a relatively new invention. What I meant by ‘thing-of-the-past’ for joint clips was for “production shops”. The clips are ‘labor intensive’ to install and one has to be careful not to damage the frame when doing so. Most pro shops would still use the “clips” because they wouldn’t want to invest in a biscuit cutter or an air/electric brad nailer, the training on how to use them and new assembly jigs.
Like you, if you only assembled one (1) frame per week, per month, etc. it wouldn’t be worthwhile to go “hi-tech” per say. Like me, I use to use clips, dowel pins, tongue n’ groove and/or mortise-tendon joints for all fixin & finishin & constructin …… but when I decided to build a large 3-piece entertainment center I purchased a “biscuit cutter”. Now that little baby takes all he guess work out of putting 2 pieces of wood together and it probably saved me a couple hundred hours of “constructin time” when I built said ‘center’. Of course, after I purchased the ‘cutter’ and became proficient in its use, ….. it was my “jointer” of choice for bout anything I did. Those 3 hour jobs became 10 minute ones. A zip zip, glue glue and done, …. a strong joint and in perfect alignment.
Anyway, I believe most 19th and 18th century frames (the 4 corner joints) were connected using either dowel pins, rib joint (2 grooves w/wood spline) or clips. The really large/wide frames always used dowel pins because that makes a stronger joint. When you can’t see how the frame corner joint is connected then you can assume it is via dowel pins. Some frames used 2 or 3 different types of molding for “effect”, one on top the other, and these were affixed using wee small nails. I probably still have a few “square nails” in a drawer somewhere that are bout 1”, ¾” and ½” long.
Boy, I got mouthy this morning. I hope my rambling was of some value to you.