There’s no “best” setup for Followers. One build may favor one follower for pushing while like the skills of other for speedfarming or bounties. First determine which Follower you synergize with while pushing, then adorn the others depending on the task.
For example your class might like Scoundrel for pushing depending on your build as his Night’s Veil is awesome but you may also keep a Templar equipped for bounties and Nephalem Rifts as he’s really durable with non-invulnerability tokens thanks to his shield. You may also have an Enchantress for speedfarming mid-high GRs for example because she’s really flexible with weapons and has an awesome IaSpd% aura for improved crowd control.
This Follower of choice for pushing GRs, also can apply on different terms. Where as your build are too dependent on cooldowns, you pick Enchantress for the push. Else, your build appear to be position dependent (channelling, long wind-up or short effective range), you pick Templar to guard and heal you often by equipping him CdR% (ie. Captain Crimson’s) gear. This becomes more and more prevalent as you push and realize which monsters can counter your build or cause loss of control on your cast cycles.
If your pushing Follower have Flavor of Time then, it’s no harm that other two have Overwhelming Desire, Dovu Energy Trap or Ess of Johan for crowd control and tightening the crowd for area damage. You avoid equipping those latter ones at pushing Followers because you want to keep the aggression on yourself. Hence you give pushing Followers minimal or very short ranged crowd control effects but allow them to sustain it with IaS%.
Your speedfarming Follower can wear Avarice Band and Wyrdward for goldfarming, or RoRG and Krede’s Flame to combine Sage’s with Cain’s. All the while pushing Follower sticks to Unity and Oculus instead.
If your pushing Follower have Nemesis Bracers, then your other Followers can have a Strongarm, Lacuni, Custerian or even Sanguinary for fun. Your Nephalem Rift running Follower can enjoy Gloves of Worship and Blind Faith or Broken Crown but you can experiment on different combinations; such as Archew’s, Sherma and Guardian’s pieces too.
Yet, it’s always better to make space for some attack speed somewhere for pushing setups. Cain’s Set offers IaS% on its Set bonus; so main reason of using Cain’s is not its experience boost nor extra key drop chance. This also saves you from having to use too many IaS% items like Mempo, Tal Rasha’s chest, Lacuni’s and Witching Hour on the Follower unless it’s necessary for crowd control.
Really, there’s no best Follower build, but there’s best Follower for different tasks for each build. You just have to decide which Follower fits your build for a push to determine that first. If you are split between two, you’re not there yet.
Also see this guide:
https://d3.maxroll.gg/resources/follower-mechanics
And other specific build guides on that site which they also give insight about Followers.
Seen it before, but it suggest what I don’t want as mentioned in the OP.