In this article I'll be comparing the Sony FE 100-400mm F4.5-5.6 GM OSS lens with the Sony FE 70-200mm F2.8 GM OSS II with the 2x teleconverter attached.
Should I get the Canon EF 70-200mm f/2.8L IS II and 2X Extender or the EF 100-400mm f/4.5-5.6L IS II Lens?
Review: Sony GM 100-400 f/4.5-5.6
FE 70-200 mm F2.8 GM OSS Mark II - Pro Photo
Sony 100-400mm f4.5-5.6 GM OSS FE - Lens – Kamerastore
Sony FE 70-200mm F2.8 GM OSS II review - Amateur Photographer
Sony FE 100-400mm G Master vs Sony FE 70-300mm F4.5-5.6 G OSS — Frank Lau Photography
The 70-200mm Lens You Won't Believe: We Review the Sony FE 70-200mm F/2.8 GM OSS II
Sony 70-200 F2.8 GM II + 2x Tele VS Sony 100-400 GM AF Comparison With the Sony A7 IV
Sony Alpha Blog : Sony FE100-400 GM: Part 6 – Comparison with 70200GM + TC & 70300G
The Sony 100-400mm Lens Thoughts and Field Test
Tamron 50-400mm f4.5-6.3 Di III VC review
Sony FE 200-600mm F5.6-6.3 G OSS - Wikipedia
Sony 100-400mm GM OSS Review
Sony FE 70-200mm F2.8 GM OSS II Review
Gear Review: Sony 200-600 f/5.6-6.3 G Telephoto Lens