I knew that would be the case and its nothing surprising. Sony A9 is the same. Its more the lenses' limitations than the body itself. Not much one can do about this. Canon does have the advantage that most of their RF lenses are coming out with 20fps in mind unlike Sony ones.
If i can get about 8fps reliably I'd be happy. 10-12fps would be cherry on the cake.
20fps is a pig to cull. My A9 was on medium all the time.
Finally found information on the compatible lenses in regards to FPS, still need to get information on 3rd party lenses as there are quite a few owners of the Sigma 150-600 amongst others out there.
EF Lenses Supporting 12 Shots/Sec. Continuous ShootingWith the drive mode set to [](High-speed continuous shooting+), the EF lenses with which 12 shots per second is possible are as follows (as of July 2020).
EF24mm f/2.8 IS USM
EF28mm f/2.8 IS USM
EF35mm f/1.4L II USM
EF35mm f/2 IS USM
EF40mm f/2.8 STM
EF50mm f/1.8 STM
EF85mm f/1.4L IS USM
EF100mm f/2.8L Macro IS USM
EF300mm f/2.8L IS II USM
EF400mm f/2.8L IS II USM
EF400mm f/2.8L IS III USM
EF400mm f/4 DO IS II USM
EF500mm f/4L IS II USM
EF600mm f/4L IS II USM
EF600mm f/4L IS III USM
EF8-15mm f/4L Fisheye USM
EF11-24mm f/4L USM
EF16-35mm f/2.8L III USM
EF16-35mm f/4L IS USM
EF24-105mm f/3.5-5.6 IS STM
EF24-105mm f/4L IS II USM
EF24-70mm f/2.8L II USM
EF24-70mm f/4L IS USM
EF70-200mm f/2.8L IS II USM
EF70-200mm f/2.8L IS III USM
EF70-200mm f/4L IS II USM
EF70-300mm f/4-5.6 IS II USM
EF70-300mm f/4-5.6L IS USM
EF100-400mm f/4.5-5.6L IS II USM
EF200-400mm f/4L IS USM Extender 1.4x
EF-S24mm f/2.8 STM
EF-S35mm f/2.8 Macro IS STM
EF-S10-18mm f/4.5-5.6 IS STM
EF-S15-85mm f/3.5-5.6 IS USM
EF-S18-55mm f/3.5-5.6 IS STM
EF-S18-55mm f/4-5.6 IS STM
EF-S18-135mm f/3.5-5.6 IS USM
EF-S18-135mm f/3.5-5.6 IS STM
EF-S55-250mm f/4-5.6 IS STM
When the Shutter Mode is set to [Electronic]During continuous shooting, if the following conditions are satisfied, high-speed continuous shooting (maximum burst of 20 shots per sec.) is performed.
- The lens is set to maximum aperture except for when using an EF-S lens*.
*For details on the lenses, see "List of lenses that the continuous shooting speed of max. approx. 20 fps less likely to decrease".
- The continuous shooting speed may change in response to the shutter speed, aperture, aperture status during continuous shooting, subject conditions, brightness (shooting in a dark environment, etc.), type of lens, etc.
List of lenses that the continuous shooting speed of max. approx. 20 fps less likely to decrease This is the list of lenses that the continuous shooting speed of max. approx. 20 fps is less likely to decrease (as of July 2020).
RF15-35mm F2.8 L IS USM
RF24-70mm F2.8 L IS USM
RF24-105mm F4 L IS USM
RF24-240mm F4-6.3 IS USM
RF28-70mm F2 L USM
EF14mm f/2.8L II USM
EF20mm f/2.8 USM
EF24mm f/1.4L II USM
EF28mm f/1.8 USM
EF35mm f/1.4L USM
EF50mm f/1.2L USM
EF50mm f/1.4 USM
EF85mm f/1.2L II USM
EF85mm f/1.8 USM
EF100mm f/2 USM
EF100mm f/2.8 Macro USM
EF135mm f/2L USM
EF135mm f/2L USM + Extender EF1.4x III
EF135mm f/2L USM + Extender EF2.0x III
EF200mm f/2.8L II USM
EF300mm f/2.8L IS USM
EF300mm f/2.8L IS II USM + Extender EF2.0x III
EF300mm f/4L IS USM + Extender EF1.4x III
EF300mm f/4L IS USM + Extender EF2.0x III
EF400mm f/4 DO IS USM
EF400mm f/4 DO IS II USM
EF400mm f/4 DO IS II USM + Extender EF2.0x III
EF400mm f/5.6L USM
EF400mm f/5.6L USM + Extender EF1.4x III
EF400mm f/5.6L USM + Extender EF2.0x III
EF500mm f/4L IS USM
EF500mm f/4L IS II USM
EF500mm f/4L IS II USM + Extender EF2.0x III
EF600mm f/4L IS USM
EF600mm f/4L IS II USM
EF800mm f/5.6L IS USM
EF800mm f/5.6L IS USM + Extender EF1.4x III
EF800mm f/5.6L IS USM + Extender EF2.0x III
EF8-15mm f/4L Fisheye USM
EF16-35mm f/2.8L III USM
EF16-35mm f/2.8L II USM
EF16-35mm f/2.8L USM
EF16-35mm f/4L IS USM
EF17-40mm f/4L USM
EF24-105mm f/4L IS II USM
EF24-105mm f/4L IS USM
EF24-70mm f/2.8L II USM
EF24-70mm f/2.8L USM
EF24-70mm f/4L IS USM
EF28-105mm f/3.5-4.5 II USM
EF28-300mm f/3.5-5.6L IS USM
EF70-200mm f/2.8L IS USM
EF70-200mm f/2.8L IS II USM
EF70-200mm f/2.8L IS II USM + Extender EF2.0x III
EF70-200mm f/2.8L IS III USM
EF70-200mm f/2.8L USM
EF70-200mm f/4L USM
EF70-200mm f/4L USM + Extender EF1.4x III
EF70-200mm f/4L USM + Extender EF2.0x III
EF70-200mm f/4L IS USM
EF70-200mm f/4L IS II USM
EF70-200mm f/4L IS II USM + Extender EF1.4x III
EF70-300mm f/4-5.6 IS II USM
EF70-300mm f/4.5-5.6 DO IS USM
EF100-400mm f/4.5-5.6L IS USM
EF200-400mm f/4L IS USM Extender 1.4x
EF200-400mm f/4L IS USM Extender 1.4x + Extender EF1.4x III
EF200-400mm f/4L IS USM Extender 1.4x + Extender EF2.0x III
EF200-400mm f/4L IS USM Extender 1.4x: With built-in Ext.1.4x + Extender EF1.4x III
EF200-400mm f/4L IS USM Extender 1.4x: With built-in Ext.1.4x + Extender EF2.0x III