Select a.*, coalesce(x.guid,y.guid,z.guid) as guid
from TableA a
left join TableX x
  on a.ProductId = x.ProductId
  and a.ProductTypeId = x.ProductTypeId -- 1
left join TableY y
  on a.ProductId = y.ProductId
  and a.ProductTypeId = y.ProductTypeId -- 2
left join TableZ z
  on a.ProductId = z.ProductId
  and a.ProductTypeId = z.ProductTypeId -- 3
left join other items of variation with where clauses at end...

Select b.*,coalesce(x.guid,y.guid,z.guid) as guid
from Tableb b
left join TableX x
  on b.ProductId = x.ProductId
  and b.ProductTypeId = x.ProductTypeId -- 1
left join TableY y
  on b.ProductId = y.ProductId
  and b.ProductTypeId = y.ProductTypeId -- 2
left join TableZ z
  on b.ProductId = z.ProductId
  and b.ProductTypeId = z.ProductTypeId -- 3
left join other items of variation with where clauses at end...

left joinTableX x
  on a.ProductId = x.ProductId
  and a.ProductTypeId = x.ProductTypeId -- 1
left join TableY y
  on a.ProductId = y.ProductId
  and a.ProductTypeId = y.ProductTypeId -- 2
left join TableZ z
  on a.ProductId = z.ProductId
  and a.ProductTypeId = z.ProductTypeId -- 3
left join other items of variation with where clauses at end...

create view view_you_need as
select
    all relevant columns
    from TableX x
    left join TableY y
      on x.ProductId = y.ProductId
      and x.ProductTypeId = y.ProductTypeId -- 2
    left join TableZ z
      on x.ProductId = z.ProductId
      and x.ProductTypeId = z.ProductTypeId -- 3
    left join other items of variation with where clauses at end...

declare @sourcetable varchar(100) = 'TableB';
declare @sql nvarchar(max);

select @sql =
'select
    all relevant columns
 from ' + @sourcetable +
' left join view_you_need
 on etc etc';

exec(@sql);