Do I need to buy ipad pro m4 16 gig of ram

Having 16GB of fast RAM storage is always preferable to having "only" 8GB - as this will always aid performance. Due to the internal system architecture, the iPad not only benefits from twice the quantity of RAM, but with 2x 8GB RAM chips also benefits from dual-channel RAM - further boosting overall system performance.

16GB RAM is only available with the 1TB/2TB models of iPad Pro - and will therefore also benefit from additional internal storage over the models will less storage.

Whether or not you "need" the additional performance benefits is something only you can decide - but choosing the higher performance option provides access to higher performance as your needs evolve over time. Many Users intentionally choose the 1TB model to benefit from increased RAM, while keeping the relative cost sensible.

Also consider the functional differences between WiFi Only and WiFi+Cellular models of iPad. Aside from the obvious Cellular functionality, only WiFi+Cellular models include GNSS/GPS location capabilities - which may impact any Apps or features that require accurate and consistent location data, such as Mapping. 

Purchase of a WiFi+Cellular model provides access to precise location services, but does not commit you to using Cellular connections. WiFi Only models of iPad have no Cellular or GNSS/GPS functions at all.

I think you’re probably border line on your usage. My personal experience with a 12.9” iPad Pro 1TB and 16GB it may be overkill, but certainly future proofs your purchase for a while.

I use Adobe Lightroom, Adobe Photoshop, and have 475 tabs open in Safari, and only 5 apps open. Safari is fluid and I could be watch YouTube in a floating window if I wanted. OK, I’m a show off, YouTube is playing an Apple video about Apple Intelligence.