You are allocating very modest amounts of RAM per server. Some servers should be OK (for a lab environment), but you are likely to run out of 8 gig on a SAS mid-tier server, and on possibly also on RTDM runtimes.
Also 100GB of storage on each tier may be ok for a SAS depot + installation + configuration (even sometimes on a thin margin) but will most likely prevent you from doing configuration backups as you progress through the deployment. I'd go with 150 minimum.
Everything else is OK but may be extraneous, depending on your usage goals for a lab environment. If it's just to get a grasp on the software and its functionality you may not need all 7 servers and might be ok with a simple single-server deployment (or a single-server design + single-server runtime). If you want to practice solution deployment in a very similar configuration to the one used with the customers in production the it makes some sense. Even though, for a lab environment you should probably focus on not running out of RAM and Storage (that you are short of), while CPU resources make much less of a difference - unless your goal is to engage in thorough performance testing.
Good luck and have fun!
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Dmitriy Alergant, Tier One Analytics