I just think you leave yourself ’blind’ without a simple inexpensive tester.
For most of us, we don’t know detailed measurements. When something is amiss, quickly check tube: short? strength? strength matched to other ’matching’ tubes?
Buy new or used tubes, test them, supposedly matched tubes, test them.
IF you are tempted by the simple type, like the Accurate 257, I will have my friend check the booklet to verify it can test your tube types.
I look for shorts, and strength on the meter, and if strength matched. As I said, my Accurate Strength always matched the big heavy Jackson’s results, so I gave the Jackson away.