multiple managed servers means the applications are divided into multiple web application servers, running in different JVMs on different ports. There is still only ever 1 copy of each.
You would have
SASServer1_1
SASServer2_1
SASServer12_1
(which numbered servers you have, varies based on what products you have installed)
Horizontal clustering means you have more than one machine hosting middle tiers (which from your description sounds like a no).
You do have multiple copies - just not on the same machine
So midtier #1 would look like
SASServer1_1
SASServer2_1
SASServer12_1
And midtier #2 would also have
SASServer1_1
SASServer2_1
SASServer12_1
Vertical clustering means you have multiple copies of a server on a single host,
eg,
SASServer1_1
SASServer1_2
SASServer2_1
SASServer2_2
SASServer12_1
SASServer12_2
The best file to check is LevX/Web/WebServer/conf/sas.conf
It will list every application, and what server(s) are serving it.
So when you search for "BalancerMember", you will find various proxy stanzas, and in a non clustered deployment, each stanza will only have one member, in a clustered setup, you would find multiple balancer members per each proxy.
BalancerMember
Not clustered:
<Proxy balancer://hostname_Cluster1>
BalancerMember ...
...
</Proxy>
Clustered:
<Proxy balancer://hostname_Cluster1>
BalancerMember ...
BalancerMember ...
...
</Proxy>