I get it, so you're interested in videogame character rips as free FBX files. But, like I said, search-engine search and "where can I find" requests are talents to cultivate. Because... then you'd find that DVa from Overwatch is actually available ready-made and rigged for Poser, and she is even able to take standard Victoria 4 ("V4") Poser action poses. Her texture is low-res, but could be up-rezed with GigaPixel AI. FoRender has DVa available as "OV DAV 01" for $15 for Poser and she comes with her OV DAV pistol. Also on the same store are a matching OV Hover Bike and Mech for Poser. Here's a quick sketch-paint + lineart render of her from Poser 11:

As you can see - fuzzy low-rez decals on the suit, and I didn't fix the loose pistol-grip.

I don't see Soldier: 76 from Overwatch at the same store yet, but there is "MK SubZero" which is a bit similar but older, and might be adapted. I can't link FoRender here, as links to other stores and sites are not allowed. Not free from there, obviously, but such things would save you weeks of time re: learning Poser rigging.

As for walk cycles being an advanced and complex thing, Poser is not Blender (where, it often seems, you're expected to make everything yourself from scratch). In Poser you don't have to make your own walk-cycles. You just load a free BHV motion-captured file onto the figure and... they walk. Or boogie-woogie dance. Or make a cup of tea. A Google Search search for CMU_EcstasyMotion_BVH.zip will get you the main free set of motion-capture files, targeted for Poser and any figure that can take V4 or M4 poses. 2,600 of them, all public-domain from CMU and professionally captured. Use in Poser: T-Pose, Select BODY, Zoom out, Import BHV, Animation Palette visible, Play.

On saving OBJ to the Library as a Prop, yes... select and press the add button.

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Learn the Secrets of Poser 11 and Line-art Filters.