When cooking sous vide, will shredding the potatoes, instead of cubing them, work just as well or could it have unintentional consequences?  Context: I am trying to improve my mashed potato recipe to get more consistent results. Unfortunately, I don't have a ricer, so I have to mash them by hand. I have previously tried mashing them in the bag, but I ended up missing several cubes of potatoes. By simply starting out with them shredded, would it make it easier in the end? But I'm also concerned it might change the texture negatively. I figure it would also allow them to cook more evenly. 
Shredding the potatoes raw will release too much calcium and disrupt too many cells, similar to pureeing them. You can definitely give it a try, though the end result will likely have a firmer gelled texture more suitable for latkes or hash browns. On the plus side, you can salvage the results for those uses. You could try passing the cooked potatoes through a coarse strainer or sieve if you have those - not as fine, but will prevent major chunks.  The science behind it Raw potatoes will have certain enzymes active (pectin methyl esterases, 'PMEs') that convert pectins in the potato cell walls from one general state to another - high methoxyl to low methoxyl. PMEs and calcium naturally present in potatoes are released when the cells are disrupted from cutting, blending, shredding, etc. The pectins get converted and the low methoxyl pectins readily bind with the calcium, forming strong calcium pectinate gels. Heating inactivates the PMEs, with full inactivation around 80C, which is why cooked potatoes usually do not gum when mashed. Resources to look into:  Potato tuber pectin structure is influenced by pectin methyl esterase activity and impacts on cooked potato texture, Heather A. Ross, Kathryn M. Wright, Gordon J. McDougall, Alison G. Roberts, Sean N. Chapman, Wayne L. Morris, Robert D. Hancock, Derek Stewart, Gregory A. Tucker, Euan K. James, Mark A. Taylor, https://doi.org/10.1093/jxb/erq280 Optimization of calcium pectinate gel production from high methoxyl pectin, Hanying Duan,Xiaoyun Wang,Nima Azarakhsh,Chao Wang,Meng Li,Guiming Fu,Xuesong Huang,  https://doi.org/10.1002/jsfa.11409 Pectin methylesterase catalyzed firming effects on low temperature blanched vegetables, Li Ni, Daniel Lin, Diane M. Barrett, https://doi.org/10.1016/j.jfoodeng.2004.10.009 Extraction and characterization of pectin methylesterase from Alyanak apricot (Prunus armeniaca L), M. Ümit Ünal and Aysun Şener, https://doi.org/10.1007%2Fs13197-013-1099-3  