Recs.
Updated
This file manager offers single and dual panes, single and dual trees, a customizable interface and toolbars, extensive scripting, FTP support, themes, and a host of other features in a product that's evolved over 27 years.
SpecsUpdate
Pros
Pro Extended scripting API
The scripting capabilities of DirectoryOpus extend from version to version. You can do a whole lot of unheard stuff with that.
Custom columns, custom commands, handling events etc. just to name a few things. It even has a GUI editor to allow for custom interfaces for your file management and scripting tasks. Even though mastering it is not easy in the beginning, it's worth it in the long run.
Pro Standard and customized layouts/styles
Directory Opus includes 8 standard layouts, including Commander, Dual Horizontal, Dual Vertical, Explorer, Filmstrip, Images, Metadata and Single. In addition, users can create and save their own layouts to suit specific needs and file processes.
Pro Relative size and date graphs
Directory Opus has an option to include relative size and date graphs. These can be displayed independently, in their own columns, or nested behind the size and date columns respectively. They can also be toggled on and off with a simple button as needed.
Pro Gets updated often
Directory Opus gets updates all the time -- fixes, significant improvements and often new features are released multiple times a month. Improvement and feature requests by users are taken in consideration and you can often find your bug report resolved or improvement request fulfilled in one of the beta versions that follow soon.
Pro WSL (Windows Subsystem for Linux Support)
Script functions can be written in WSL Script, DOS Batch Mode, VBScript, JScript or directly calling Opus or External applications. /mnt/c
paths understood by path fields. WSL mode in Find As You Type (FAYT). Copy path names in WSL format or Windows format.
Cons
Con NOT FREE--as such, it shouldn't even be considered in the category of "best Free Explorer replacements."
It's $49AUD. WTF?
Con No good support for right-sided tree
The only way to get a right sided tree is to display both panes in horizontal layout and then switch the first (upper) tree off. Which leaves you with 2 horizontal panes and one tree on the right. There is no other way (neither with 2 vertical nor with 1 pane) to have a tree on the right side. And since this layout setting is rather the step-child of the developers, it also is a bit buggy and not of top priority as far as fixing any issues with it.
Con Restrictive license
Product is licensed on a "per-machine basis" requiring purchasing multiple expensive licenses to cover a single user with multiple machines.
However, if you have time and luck, you can write to the DO sales department and they can produce another license for you to use personally on another machine you own.