I also prefer Arctic Silver 5 for most CPU installations. Maybe not the very best of the best of the best but it's always counted among the top performers and it's cheap and common and - unlike most other TIMs - an application of AS5 seems to last at least a few years before it cooks off.
I also use Prolimatek PK-1 and PK-2 (I still have big jars full of the stuff) and Gelid GC Extreme (because it's so excellent for some things) and a Shin Etsu X23 (which we use for so many things at work). I sometimes even mix my TIMs together to "engineer" something more ideal for a particular application. I always mix my TIM up evenly (by vigorously shaking the tube, if nothing else) and heat it up a bit (stick the tube into warm water) before application. I scrape it across CPU parts with a razor blade, similar to the credit card method described above. Too little is far better than too much, if you have to wipe off any TIM that's leaked out of the edges then you'll find there's always "thick" spots and "thin" spots and bubbles/gaps hidden between the parts which can run too hot.
Phobya HeGrease is apparently quite good, too. And IC Diamond, although it contains abrasive microparticles which can apparently (at least over time and over repeated applications) actually scratch up the polished surfaces (and part markings) on processors.
Any premium branded TIM is going to outperform any cheap/generic TIM. And the differences between 99.5% or 99.55% or even 99.75% thermal efficiency aren't worth obsessing over unless you're going for some sort of world record overclock ... especially since there's so much controversy, bias, misinformation, disinformation, exaggeration, elaboration, and hype about which of the very best top performing brands is indeed the very best top performing brand. And one thing all those comprehensive lab benchmarks don't measure or compare is TIM longevity - I know that AS5 can last years and Gelid or X23 can last months, but I don't know how most TIMs compare in the long run - an important parameter for those of us who don't plan to remount CPUs with great frequency.
TIM coverage is far more critical than TIM conductivity. Low viscosity (thin and runny) TIMs are better used when the gap between mating part surfaces is extremely tight or interlocking part geometries makes TIM application inaccessible/difficult. High viscosity (thick and pasty) TIMs are better used when the gap between mating part surfaces needs a little bit of "filler" to maintain efficient thermal contact. Thermal pads and glues should only be used when a bulk material is needed to conduct heat across larger (air-filled) gaps and/or to provide some mechanical adhesion (structural stability) between parts. In fact, thermal pads are generally used only in situations where solid-state TIMs (like silica, mica, elastomer, HOPG, etc) cannot be used instead.
I haven't installed any Ryzen parts yet so I admit I'm unfamiliar with their specific surface features.
Other CPU parts often have slightly convex or concave surfaces. Designed to be paired with coolers which have perfectly matched slightly concave or convex surfaces - to provide greater cross-sectional area for heat transfer between the two surfaces. Although the majority of coolers are not exclusively designed to perfectly fit exactly one processor, they often have "perfectly flat" (and slightly-oversized) baseplates which are designed to accommodate a wider range of sockets and fittings and processor types. If the processor and the cooler don't "match" perfectly then a mid-viscosity TIM (like AS5) is an excellent choice, although some experimentation with different (or mixed) TIMs might be required to find an optimum heat transfer.
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