If you are a landscape shooter, then a tech cam + MFDB back is the best there is. While I like the convenience of an SLR like the DF, the lenses from SK and Rodie (especially the newer ones like the SK60XL/Rodie 32HR/90HR) are in a totally different league from anything I have shot including Leica and the P1 SK/LS line.
It sounds like you have already made this choice, so great. The IQ260 will be a great all rounder for landscape use on a tech cam from the specs and the sample files I have seen so far. The IQ160 is again the best all rounder given lens cast issues with the 180. So again, I think you are on the right track here.
When it come to tech cams, you've got the 3 major players with pancakes and some hybrids like the Arca ML2 and Techo (as discussed above by Torger, do look at his review, it is quite extensive and useful, not just on the techno, but on using MFDB on a tech cam in general). Chris B., also has some great info on his blog on both the Arca Rm3di and ML2.
I do primarily landscapes and went with the RM3Di. I use an IQ180 and have am IQ260 Achro on order that I just cannot wait to get my hands on.
The reason went with the RM3Di are as follows:
1. The company and Martin are all about engineering precision - not marketing, market share etc. This has its downfalls like no website, unknown lead-times on orders, some stuff like eModule (and cloud) that have been outstanding for 2-3 years etc. BUT, at the end of the day, when they release something it works as promised. It is all about form follows function.
2. In keeping with the above, it is a system that is open and modular -- you can use your adapter plate on a Monolith 6x9 or ML2. Same thing with any other accessories like the Rotaslide or Rotamount. You can even use the RM3Di as the front standard on the Monolith, F-line etc. The new Factum, carries on with this thinking. The RotaSlide is a marvel of engineering precision, technical execution, and creativity. I can assure you that claims that a sliding back cannot be made to the tolerance levels needed by modern MFDBs is BS.
3. The focussing system - Although the IQ180 has LV, it is not what you'd call close to what you'd find in a CMOS DSLR. I needed an idiot proof system for focussing, and the Arca system gets me this. Shimming does make a difference. with the Arca, it is simply an offset on the focussing index. I think you can get infinity accurate in all three manufacturers, but with the Arca, I can ensure that I have it calibrated so I have the maximum DoF from infinity in. Not sure if I am being clear on this, I can elaborate if needed. I shoot in some strange places, often just pulling my kayak up on a rock in the middle of nowhere, and don't usually have the time to check and recheck focus. The Arca system for me, is as idiot proof as it comes.
4. While the eModule/cloud was not available when purchased my RM, it is now slowly trickling in. I demoed a production version a couple of weeks ago, and again for me, it is a game changer in terms of controlling DoF and close focussing with large apertures. One thing you will find with the hi-res MFDB's and the near lenses, especially Rodies, is that optimal performance is in the f7-9 range. So this is important for me.
5. Why not Alpa - I think they make great high-quality gear. But I wanted Tilt in a more integrated way, so the RM made more sense. I did think long about Alpa given the multiple body options, but once the Arca Factum was announced, I had the option of a lightweight or a full featured setup. The lack of a sliding back was also a downer for me. On focussing, the HPF rings get you closer, but again, I find the precision of the Arca mount to be better. When it comes to look and feel, I think Alpa has the edge. The various options for shutter releases are also better integrated. On the other hand, all the bits and add ons for T/S, stitching etc. could be clumsy.
6. Cambo - just never connected with it. Cambo is a little cheaper and likely more in use, so you are likely to find better availability of used lenses and bodies.
Good luck with your purchase, and strongly recommend finding a good dealer for whatever option you choose. This is at best a cottage industry and dealers and their relationship with the manufactures make all the difference.