Paging and count as one query

var query = context.Artists.AsNoTracking()
    .OrderBy(x => x.FirstName)
    .Select(x =>
        new ArtistsResponse
        {
            FirstName = x.FirstName,
            LastName = x.LastName,
            Slugs = x.Slugs.Select(s => new ArtistSlugResponse { Name = s.Name, IsPrimary = s.IsPrimary }).ToList(),
            ImageId = x.Image == null ? 0 : x.Image.Id,
        });

var page = query.Paging(offset, limit) // do any filtering via `Where` here, before the paging clause,  unless you want TotalCount to take filtering into consideration
    .GroupBy(x => new { TotalCount = query.Count() })
    .First();